ADVANCED PHYSICS EXPERIMENTS
MORGAN PARK HIGH SCHOOL
CHIEF AUTHOR - R. Coleman
CO-AUTHORS - 623 Sadistic Students
1995 Edition
A Revised and CONFUSED version of all previous editions.
CAUTION
THESE EXPERIMENTS MAY BE HAZARDOUS TO YOUR HEALTH!

TABLE OF CONTENTS
INTRODUCTION

EXPERIMENT
1 - THE ACCELERATION OF GRAVITY
2 - THE ACCELERATION OF GRAVITY
3 - THE BALLISTIC PENDULUM
4 - PROJECTILE MOTION
5 - ATWOOD'S MACHINE
6 - BOUNCY-BOUNCY
7 - NEWTON'S SECOND LAW
8 - THE NON-VERTICAL PENDULUM
9 - SPHERICAL SURFACE PENDULA
10 - FRICTIONLESS ACCELERATION
11 - ROTATING MASSES
12 - STREAM VELOCITY
13 - TWO DIMENSIONAL EQUILIBRIUM
14 - THREE DIMENSIONAL EQUILIBRIUM
15 - THE YO
16 - THE MOMENT OF INERTIA OF A LONG ROD
17 - THE MOMENT OF INERTIA OF A CYLINDRICAL DISK
18 - THE GYROSCOPE
19 - BOYLE'S LAW
20 - CHARLES' LAW
21 - THE HEAT OF FUSION OF WATER
22 - THE HEAT OF VAPORIZATION OF ALCOHOL
23 - CALIBRATING A THERMOPILE
24 - THE MECHANICAL EQUIVALENT OF HEAT
25 - THE CONSTANT VOLUME GAS THERMOMETER
26 - ELECTRIC FIELD NEAR SEVERAL CHARGE DISTRIBUTIONS
27 - ELECTRIC FIELD NEAR SEVERAL CHARGE DISTRIBUTIONS
28 - THE CHARGE ON THE ELECTRON
29 - THE ELECTRIC DING-DONG
30 - THE CATHODE RAY TUBE
31 - THE POTENTIOMETER
32 - THE CHARGE TO MASS RATIO OF THE ELECTRON
33 - THE CHARGE TO MASS RATIO OF THE ELECTRON
34 - DIP ANGLE AND STRENGTH OF EARTH'S MAGNETISM
35 - DETERMINING THE INDUCTANCE OF SEVERAL COILS
36 - CAPACITOR DISCHARGE
37 - THE MUTUAL INDUCTANCE BETWEEN TWO COILS
38 - LC RESONANCE
39 - MELDE'S EXPERIMENT
40 - THE SPEED OF SOUND
41 - GUESS WHAT
42 - READING THE SCALES ON A PRISM SPECTROMETER
43 - THE WAVELENGTH OF SODIUM LIGHT
44 - THE WAVELENGTH OF LIGHT
45 - THE INDEX OF REFRACTION OF AIR AND GAS
46 - PRISM SPECTROMETER AND CAUCHY COEFFICIENTS
47 - PHOTO EMISSION AND CONDUCTION
48 - THE SIZE OF A MOLECULE
49 - BRAGG DIFFRACTION
50 - RADIOACTIVE DECAY

NASTY COMMENT
FIGURES AND DIAGRAMS
BIBLIOGRAPHY
ADDITIONAL REFERENCES

INTRODUCTION

You will be privileged to perform these experiments and will find you may even survive this course if you follow the instructions given, paying particular attention to the warnings, cautions and notes in the instructions. With the exceptions noted in the instructions, it is your responsibility to read, and know how to perform, the experiments the day before your group is to do the experiments.
The experiments are to be written up as follows: One member of each group will turn in a complete write up on each experiment with all other members turning in those parts which are marked (*). A carbon copy of these parts from the original write up is acceptable. (All examples are for some form of experiment 1.)

1. Introduction - A brief statement of what is to be found and how. Example: In this experiment the acceleration of gravity is to be determined using a free fall type apparatus with a spark timer.

2. Theory - If you are asked to, or want to, derive an equation or equations, you will use this section for that purpose. If no derivations are to be done, list the sources (book and page number) of the equations that you used.

3. Procedure - A brief statement of any deviations from the normal procedure given in the instructions is all that is necessary. If you followed the instructions reasonably closely, just state that.

4. Data - Neat tables listing the data obtained. A carbon copy of the original data sheet must be turned in after performing each experiment but before leaving and be with each member's report. It may be rewritten if the original is not as neat or clear as possible, but the original must also be turned in. (*)

5. Sample calculations - One or two clearly written out examples of how your results were calculated.

6. Results - A table giving the results you obtained and a sentence or two or table giving the averages from the many similar trials made. (*)

7. Error analysis - A brief table listing the error expected in each type of measurement, the total expected error and the actual error obtained as a percent of the theoretically expected result. If your actual error percent falls below the expected, you only need to say the error is less than expected, but if your percent is greater than expected, you must explain why, to the best of your knowledge, the expected error was exceeded. Where you are trying to compare values obtained from two equations or are trying to compare the two sides of one equation, the theoretical value will be that obtained from the equation using distance, mass or angles of the parts of the system, while the actual values will be those obtained using time related values of the system as a whole. In some cases, no theoretical value can be obtained so all that you need to do is to calculate the expected error on your results. (*)

8. Conclusions - Write a sentence or two on what can be concluded from your results.

9. Answers and comments - Answer any questions asked in the instructions and comment briefly on possible improvements to the experiment. If the instructions ask you to explain something or ask why something is as it is, use this section.

In several experiments you will be required to obtain the rate of change of some quantity from a series of data points, either recorded on spark timer paper or obtained from a progressive series of additions to previous data readings. There are many ways of evaluating this type of data, but most methods result in the net effect of only using the end points of your data. The method which you will use is the only one which allows all of the data points to be used. I call this method the method of differences and it works as follows:

Number your data points and divide them into two approximately equal groups (example - for 12 points, the first six would be in the first group and points 7 through 12 in the second). So far so good. Now, subtract successive elements in the first group from those in the second (7-1, 8-2, 9-3, etc.). Confused yet? If not, read on. Since this method will only be used to determine the rate of change of some quantity, (Ds/Dt, Dv/Dt, DF/Ds,etc.) you will need to know the other variable. When calculating any rate of change, both quantities must be over the same interval, therefore you simply (?) determine the interval for the first quantity and use the corresponding interval for your other variable (example: if you are timing and have a half second between points, the time interval between the first and seventh points is 3 seconds).

In order to ease your misery, computer programs are available to do most of your calculations. Programs for experiments 1, 7, 25, 38 and 46 will be available. It will be your responsibility to run these programs.

The experiments will be graded on an eleven point scale if they are completed and turned in within one week of the day you are assigned to do the experiment. They will be graded on a ten point scale if turned in later than one week after the assigned day, but before the final due date. If turned in on the due date, they will be graded on a nine point scale. Experiments turned in after the final due date will be graded on a ten point scale, but will be penalized two points per day (including weekends) late, up to a maximum of minus twenty.

You may replace one experiment per marking period with an original one of your own choosing. The due dates and grading are the same as for all other experiments and the same general rules apply as those listed in experiment 41. During the fourth marking period, an original, ongoing experiment, started before mid-year may be used to replace experiment 41 and one or more others, depending on the complexity and originality of your experiment (a science fair project would be a good example).

The following abbreviations will be used in describing the references: IIT lm - Illinois Institute of Technology General Physics Lab. Manual l956 H&R - Halliday and Resnick 1966 (dark blue) S&Z - Richards, Sears et. al. 1962 (grey) M - Miller 1967 (green) S - Schaumns Outline 6th ed. QC - Quick Calculus 1965

THINK - DO YOU REALLY WANT TO GO ON?


EXPERIMENT 1 - THE ACCELERATION OF GRAVITY

This experiment uses the free fall apparatus set up in the back room (the tall pipe with the heavy tripod base and spark timer). Run the wax coated paper up from the bottom and through the top of the apparatus with the wax coated side out (it should be on the front of the support pipe, just in front of the wire next to the pipe), use the chained on clip to hold it taut and position the paper slightly off center so you can make more than one run on each piece of paper. Turn on the electricity (both the large panel and the spark timer) and hang the plum-bob (the string with the bolt on one end), with the pointed end up, on the bottom of the blue magnet, point to point. Using the leveling screws at the base, center the bolt exactly between the wires. Replace the plum-bob with the falling body (pointed end up). Make sure that the timer is turned on for at least a minute and leave the master switch on until you are done with all of your trials. Slightly before one of your group members turns off a circuit breaker on the electrical panel, another member should press AND HOLD the spark switch on the spark timer. The same person should not do both as this could lead to a very shocking experience! This should produce a series of spark dots on the waxed paper and if the spark switch is held down too long, it will also produce flames which will quickly consume your data. Using the method of differences, determine the acceleration of gravity. NOTE: You will need to use this method twice, the first time to get velocity and the second to get the acceleration. Average this second set to get the acceleration of gravity. The spark timer produces 60 (0.1) sparks per second. You should make at least three trials and at least one must be worked out by hand. The other trials may be calculated using LONGESTM.

References: IIT lm 22, H&R 48, S&Z 62, M 35, S 27, QC 138


EXPERIMENT 2 - THE ACCELERATION OF GRAVITY

Use the long bar with the crossarm on one end. Support this such that it swings freely between two lab tables (you will need two support rods and one crossbar). Start the bar swinging with some initial angle (the exact angle need not be known as long as all trials use about the same angle) and, using a stopwatch, determine its period, averaging several trials and allowing the bar to make several swings each trial. Tape a strip of carbon paper and white paper to one edge of the bar. Should this affect the period? Attach a metal ball to one end of a piece of string and run the string over the top of the bar, attaching the other end through the hole at the bottom of the bar such that the ball just barely touches the floor. Pull the string, using only two fingers of one hand, so that the ball comes to the top front corner of the bar and, at the same time, the bar is pulled to approximately the same angle used previously. When you release the string, the bar should swing down and hit the falling ball, leaving a carbon spot on the paper. Since you know the time for the bar to swing to the vertical is 1/4 of the time to make one complete swing, and also the distance that the ball fell, you can easily calculate the acceleration of gravity using S = 1/2gDt2. Make several trials and use several different balls. Should the type of ball make any difference? Average your results and explain any major differences.

References: IIT lm 47, H&R 48&140, S&Z 62&229, M 35&195, S 27&84


EXPERIMENT 3 - THE BALLISTIC PENDULUM

A gun and catcher arrangement will be used for this experiment. Set up the apparatus on a level surface, remove the pendulum, determine its mass and that of the ball, determine the center of the mass of the pendulum with the ball inside, then replace the pendulum in its holder. Place the ball on the end of the gun's rod and carefully cock the gun by pushing on the ball. Use care so as not to bend the rod. Fire the ball into its catcher. The ball should stay in the catcher, with both swinging up and catching on the ratchet. If this doesn't happen, check to see if everything is carefully aligned. Measure the height increase of the CENTER OF MASS of the pendulum and ball at least five times. By knowing the mass of the ball, the mass of the pendulum, its increase in potential energy (where did this extra energy come from?) and that you had an inelastic collision, determine the average velocity of the ball as it entered the pendulum. This is your theoretical value. Next, determine the velocity of the ball from its range. Using an open area, fire the gun horizontally off of one of the tables and note where the ball lands. Tape a piece of paper at this spot, place carbon paper on top of this so that when you fire the ball for five trials, five carbon spots will be left on the paper (NOT the floor). By knowing the height of the gun and the distance from the spots to a point directly below the end of the rod, you can also determine the average velocity of the ball. For a second check, tilt the gun upward. Shooting from the back of the table so the gun rod doesn't hook, find the range (from the end of the rod), height from the floor to the end of the rod and angle of the gun (if you're careful, a 30o angle is useful) determine the average velocity using five trials. Explain any major differences.

References: IIT lm 41, H&R 219, S&Z 167, S 63


EXPERIMENT 4 - PROJECTILE MOTION

A steel ball is allowed to roll down an inclined tube with an inclined lower end. The object of this experiment is to use your vast knowledge of physics to show that you can calculate where, within experimental limits (which are what?), the ball will land. Use a level to determine the angle of the lower part of the tube. Measure the height of the top of the tube above the bottom of the tube and the height of the lower end above the floor in centimeters, including any estimated uncertainties. Calculate Vo (the velocity as the ball leaves the tube) using the law of conservation of energy. Calculate how far horizontally from the lower end of the tube the ball should land. Tape a piece of paper on the floor above the landing site and put a piece of carbon paper over the spot and roll the ball down the tube. If the ball landed more than a few centimeters away from the calculated spot, find other factors not previously considered and repeat the calculations. Your experiment is complete when your calculated spot agrees with what you obtained experimentally.

References: H&R 59&272&281, S&Z 104, M 44, S 31, IIT lm 45


EXPERIMENT 5 - ATWOOD'S MACHINE

Atwood's machine is just a horrifying name for a set of freely moving masses attached by a string over a pulley. The equation which you are to derive is a = ((m1-m2)g/(m1+m2))+af where a is the acceleration of the system, m1 and m2 are the masses and af is a fictitious acceleration due to friction. Hang several masses (m1) on a string passing over the pulleys in the front of the room and balance these with a like amount of mass (m2) on the other end. The total mass (m1+m2) should be 600g - 1100 g. Throughout the entire experiment, m1+m2 MUST remain constant. The string should be somewhat longer than the distance from the floor to the pulleys. Remove some mass from one side and add it to the other. Release the system and time its fall. Using S = 1/2aDt2, a may be found. Do this several times, averaging your results. Now, take more mass off of the light side and add it to the heavy side and repeat the process. Make several different trials with different mass distributions. You will note that when m1-m2 becomes large, the smaller weight may fly off when it reaches the top, therefore you should either be clear of other groups and especially observant so you don't get hit, or supply everybody with hard hats. To find af, make a graph of a vs. m1-m2, the point where this straight line (if it isn't straight, explain why) crosses the a axis is af. Using this value, check each previous set of data for accuracy. a is your actual value since it was found by measurements on the complete system, while the right side of the equation is the theoretical value since it involves the measurement of parts of the system.

References: IIT lm 22, H&R 101, M 66, S 41


EXPERIMENT 6 - BOUNCY-BOUNCY

The period of oscillation of an object bouncing on a spring will be obtained physically and theoretically in this experiment. The experiment will use a spring, a number of 50 and 100 g masses, a meterstick and a timer. Suspend the spring and attach enough weights to separate the coils slightly. Use this position as your starting position. Take ten readings, increasing the mass on the spring by the same amount each trial and record the mass, weight and position relative to the starting point. Use the method of differences to determine the force constant of the spring, DF/Ds=k and average these. Attach 300g - 700g to the end of the spring and start it oscillating up and down. Accurately determine the period, possibly averaging several trials of 20-30 cycles each. Do this for at least three different masses. Determine the mass m' of the spring. Calculate the theoretical period of the spring using the equation (which you will derive) T = 2pi*sqrt(((m'/3)+m)/k). Compare these values with those obtained with a timer.

References: IIT lm 32, H&R 345, S&Z 217-218, M 187, S 83, QC 122&272


EXPERIMENT 7 - NEWTON'S SECOND LAW

Here it is folks, your chance to prove (or disprove as the case may be) that infamous equation F=ma. Your apparatus consists of a heavy cart, its track, several masses and the same spark timer used in experiment 1. Support the track high enough off of the floor so that the small wire used to pull the cart will just reach the floor as the cart reaches the end of the track. Then level the track. Fasten the waxed tape across the top somewhat off center (so one tape can be used for several runs) between the points on the cart. Hook the spark timer to the track and the terminal on the pulley support. The ground wire should go to the track. Place 200g on the cart and 100g on the wire. Release the cart and start the timer. Unless you would like a large charge from this experiment, different members of the lab group should release the cart and start the timer. Repeat this with 150 on the wire and 150 in the cart. Try a third run with 200 on the wire and 100 in the cart and finally, use all 300g on the wire. You must determine the acceleration for each of these trials in a manner similar to experiment 1. One trial must be done by hand while the rest may be run through the computer using LONGESTM. Note: you don't need to use every point, every 6th, 10th, or 30th is OK as long as you use the corresponding time interval and have at least 16 data points left. Plot a vs. F on a graph, the point where this line crosses the F axis is the frictional force. Since a = F/m, the slope of this graph should be 1/m, where m is the total mass being accelerated. This slope gives you a theoretical value for m. Subtracting the frictional force from the force on the end of the wire, calculate the acceleration in each trial and compare this value to the actual acceleration of the cart.

References: IIT lm 25, H&R 85, S&Z 83, M 58, S 35, QC 138


EXPERIMENT 8 - THE NON-VERTICAL PENDULUM

This is a swinging experiment. Use a table in the front of the room with a frictionless puck attached to the edge by a string 1 meter long. In order to eliminate interference, run the air hose through a clamp mounted about a half meter above the edge of the table. Tilt the table 4o-6o, turn on the air and determine the period of oscillation. Tilt the table more by putting books under the legs. As the slant becomes greater, support the table from the other side. Plot a graph of period vs. angle, using at least 25 points. Knowing that the period should be T=(f(theta))*(2pi sqrt(L/g)), guestimate what f(theta) should be, then go back and plot this theoretical graph on the same paper as the experimental graph, explaining any differences.

References: QC 9&38


EXPERIMENT 9 - SPHERICAL SURFACE PENDULA

Part 1: Using balls of various radii (at least three different), allow them to roll back and forth in two bowls of different radii, keeping the amplitude small so that no sliding takes place. What would happen to your results if they did slide? Record the radius of the ball r, the radius of the surface R and the period. Calculate the period using T = 2pi sqrt[(7(R-r))/5g] (which you will derive) and compare this theoretical value with your experimental value. You will need to use a spherometer to determine the radii of the bowls, so a bit of research before coming to class would be helpful. Part 2: Using the short air track and small carts, clamp the center down and allow the cart to oscillate back and forth, timing the motion. Prove experimentally and theoretically that this period is equal to the period of a pendulum whose length is that of the radius of curvature of the track.

References: IIT lm 109, H&R 118, S&Z 117


EXPERIMENT 10 - FRICTIONLESS ACCELERATION

With the air track apparatus, (air track, vacuum and variac, keeping the pressure just high enough to allow the cart to float freely) determine the acceleration of the cart for various angles of elevation of the track using S = 1/2at2. Derive an equation for the acceleration in terms of the angle (or some function of the angle) of elevation. Note: A protractor or angle finder is not accurate enough and you should consider how to find the sine of the angle using only a meterstick. Does the mass of the cart make any difference? Using the cart with the water container on it, check the direction of 'down' in this accelerated reference frame and attempt to justify your findings. DO NOT let the water cart hit the end of the track. Your angles should generally be less than 2o-4o.

References: S 43


EXPERIMENT 11 - ROTATING MASSES

Obtain a turntable, the T holder and a small mass. Attach the mass to the T holder using some suitable length of string (L) and allow it to rotate. Using your vast (?) knowledge, determine experimentally the angle (theta) that the cord makes (describe your procedure). Derive an equation giving the angular velocity of the turntable in terms of L, and r (the distance from the center or the holder to the hook). Note: You will probably get an equation giving the angular velocity in radians per second. In order to convert to revolutions per minute, multiply by 30/p. Average your values for the same turntable speeds but different arm lengths and compare these with the actual turntable speeds. (You should have 4 trials for each of 4 speeds.)

References: H&R 66, S&Z 112, M 155, S 71


EXPERIMENT 12 - STREAM VELOCITY

This experiment is all wet. Use the plastic container with three holes in the side, the top with the tube and the tank to catch the water. Plug the two top holes and place the stopper with the eyedropper in the bottom hole. Fill it almost full with water and place the top on it with the tube 4-7 cm. below the surface of the water. Use a sealer to seal the top. When water is allowed to flow out of the eyedropper, its velocity should be constant (prove it). By using the equations given in the reference, you will be able to determine the velocity of the stream as it leaves the dropper. Note: the surface of the water is considered to be where the air is entering. You should also find the velocity by using the height and range as you did in previous experiments. Explain any differences.

References: H&R 458 (prob. 9), S&Z 207, M 260, S 94


EXPERIMENT 13 - TWO DIMENSIONAL EQUILIBRIUM

Using the force table supplied, balance three UNEQUAL forces such that their point of application is directly over the center pin. Prove graphically and algebraically that the resultant of these forces is equal to zero. For a second trial, use four UNEQUAL forces, proving algebraically and graphically that the resultant of three of these is the equilibriant of the fourth. No error analysis is necessary but if the sum is not zero, explain. In general, what can be said about any one force acting on a point in equilibrium if there are n-l other forces also acting on this point?

References: IIT lm 36, H&R 320, S&Z 20, M 86, S 1, QC 25


EXPERIMENT 14 - THREE DIMENSIONAL EQUILIBRIUM

Arrange at least three spring balances on two or more different supports such that you have lines running from the balances to some common point between them and hang at least 10 nts. from this point. The balances can be tied to any point as long as the lines do not fall in the same plane. Use your imagination to construct a system. Prove either algebraically or graphically that any one of the forces is equal to the vector sum of all of the others. If you solve your system algebraically, comment on the geometric solution and, likewise, if you solve your system graphically, comment on how you could also solve it algebraically. Comment on the problems encountered when measuring angles in three dimensions. Sketch your arrangement.

References: IIT lm 36, H&R 320, S&Z 20, M 86, S 1, QC 25


EXPERIMENT 15 - THE YO

Your apparatus for this experiment is two large pieces of masonite, one round, the other square, a meterstick, caliper and timer. Hang the disk such that it will roll down and back up without touching the string. Knowing the time it takes to go down and back up, (the average of several trials) using one half of the total time to compensate for the frictional forces and also, by counting the number of turns it makes going down and back up, again using one half of this number, you can calculate the angular acceleration of the disk on its way down. You should justify the use of a half of the time and turns in your error analysis. The torque can also be calculated by taking the weight of the disk times the moment arm (the radius of the axle plus the radius of the string). Why is the radius of the string used? Using the rotational equivalent of Newton's Second Law, the radius of gyration of the disk may be found (you only need to find the radius of gyration). Note: If you solve your equations symbolically first, you should find that you don't need the mass of the object. The radius of gyration may also be calculated using the physical properties of the disk. Repeat the above using the square.

References: IIT lm 27&45, H&R 286, S&Z 179&183-186, M 156&165, S 67&75


EXPERIMENT 16 - THE MOMENT OF INERTIA OF A LONG ROD

With the rod and axle, metal rails with supports and several weights, you will determine the moment of inertia for a long thin rod. Set the rod so that it rolls on its axle along two rails. Hang a weight on the end of the string, allowing the rod to rotate freely from rest and time one revolution. Calculate the average angular velocity of the rod during this one revolution. Do this for 2, 3, 4, etc. revolutions, measuring the time for each respective number of revolutions and calculating the average angular velocity during this interval. (Where, during the time interval for each trial, does the average occur?) Plot v vs. t, noting that the line is not straight, but curves as the number of turns increases (why?). By taking the slope of this line at its straightest interval, the angular acceleration can be obtained. Do this for several different weights and plot on another graph, weight vs. acceleration. The point where this graph crosses the weight axis is the frictional force. As in experiment 15, the moment of inertia may be found since you know the angular acceleration and torque. Calculate the moment of inertia for each weight used and average your results. From this average, determine the radius of gyration of the rod. Obtain a theoretical value from the physical properties of the rod for the radius of gyration and moment of inertia.

References: IIT lm 27&45, H&R 286, S&Z 179&183, M 156&165, S 67&75


EXPERIMENT 17 - THE MOMENT OF INERTIA OF A CYLINDRICAL DISK

Happiness is finding an easy experiment. Better luck next time. The apparatus for this experiment is set up in the project room. You should notice that there is a heavy steel disk with a string attached to its axle and passed through a pulley for this experiment. Place a weight (W) on the end of the string large enough to accelerate the disk (about 5-10 Nts.) and allow the weigh to fall, timing the fall. Do this at least three times for the same weight and distance (h) of fall. Average these three trials (the times of fall and return height). Repeat the above procedure with three different weights. Average these trials, their times and distances of fall. Using S = 1/2at2, find the linear acceleration of the descending weight. This is also the tangential acceleration of any point on the axle. Find the frictional forces acting on the disk by allowing the weight to rise again during each trial. Measure the return height (h'). The frictional force is then given by f=W(h-h')/(h+h') which you should derive by knowing that the loss in potential energy equals the work done by friction. Note: all distances are measured from the lowest point in the travel of the weight. The acceleration force (F) is just the weight minus the frictional force. Therefore the accelerating torque is Fr where r is the radius of the axle plus the radius of the string. Since the radius r and the tangential acceleration are known, the angular acceleration may be calculated using alpha = a/r. Therefore, the moment of inertia (I) may be found from I=Fr/alpha. As a check, and to obtain a theoretical value, the moment of inertia should be calculated using I = 1/2MR2. Here, R is the radius of the disk and M is the mass of the disk. The mass must be calculated by multiplying the disk's volume by its density (7.83g/cm) since you may NOT remove the disk for direct measurement of its mass. The disk's radius is 4 inches. The most common error in this experiment is having inconsistent units.

References: IIT lm 27&45, H&R 286, S&Z 179&183, M 156&165, S 67&75


EXPERIMENT 18 - THE GYROSCOPE

The purpose of this experiment is to study the motion of a gyroscope. The apparatus consists of a bowling ball rotating in a socket and two timers. Friction is reduced by supporting the ball on a thin film of air. On the ball is mounted a removable steel shaft. The system is set into rotation by spinning it with your hand and the average number of revolutions per minute is obtained with the help of a timer. The period of precession is simultaneously checked with another timer. The equation you will attempt to verify is: tau (Torque) = w (angular velocity of precession) X L (angular momentum of the system). Since the angular momentum of the ball is much greater, we can neglect the rod and express this equation as (f/T)=(3.799)(m1r1)g/(MR2). You should derive this in your report. Here f is the average rpm for each trial, T is the period of precession, m1 the mass of the shaft, r1 the distance from the center of the ball to the center of the shaft. M is the mass of the ball and R the radius of the ball. Use the right side of the equation as the theoretical and the left side as the experimental values. The average rpm should be the number of revolutions divided by the time (in minutes) of precession. CAUTION!!!!! Should the air be suddenly cut off or the ball not started correctly, it is possible for the ball to gyrate erradically, geometrically building up until either the ball pops out of the socket or the rod flies out. Therefore, should the ball start to wobble, reach in and gently steady it or duck!!

References: IIT lm 27&45, H&R 286, S&Z 179&183&195, M 156&165&179, S 67&75


EXPERIMENT 19 - BOYLE'S LAW

You are to, with the aid of a graph, show that Boyle's Law checks within the limits of experimental error.

References: H&R 433&572, S&Z 350, M 305, S 114


EXPERIMENT 20 - CHARLES' LAW

Obtain a boiler stand, burner, thermometer, glass tube with mercury bead, ice (or snow) and salt. Mix the ice (or snow) and salt in the boiler to obtain a mixture 5-10oC below zero. If you are using snow, alternate layers of packed snow and salt and add about 250ml of cold water when you have the boiler full. Insert the glass tube and thermometer through the two hole stopper, keeping the thermometer bulb even with the midpoint of the lower portion of the glass tube. Why? Plot a graph of height of bead vs. temp. as the mixture is heated. What difficulties were encountered in measuring the height of the bead? Extrapolate your graph down to zero height. What temperature does this represent? Why do the top and/or bottom points not fall along the general line of the other points? Note: Thoroughly rinse off all of your equipment after the experiment as the hot salt water causes very rapid rusting.

References: M 317, S 114


EXPERIMENT 21 - THE HEAT OF FUSION OF WATER

You are to, with the aid of a perfectly insulating calorimeter (styrofoam cooler), determine the heat of fusion of water. You should have about 1000g of water and must use ice, snow won't work. (why?)

References: IIT lm 88, S&Z 310, M 292, S 124


EXPERIMENT 22 - THE HEAT OF VAPORIZATION OF ALCOHOL

Here is an experiment to get you steamed up. Determine the heat of vaporization of alcohol. CAUTION ---- Alcohol is highly combustible. Insert a thermometer in the boiler and heat with a low flame until the temperature reaches the boiling point (how can you tell?). While you are heating the alcohol, the outlet tube should be immersed in some extra water and the tube should be watched so it doesn't kink and allow the internal pressure to build up as these vapors are explosive. (BOOOMMMMMM!!!!) While it is boiling, insert the outlet tube into the calorimeter water, keeping it away from the styrofoam.

References: IIT lm 86, H&R 563, S&Z 310, M 292, S 124


EXPERIMENT 23 - CALIBRATING A THERMOPILE

Using the thermopile supplied, attach the chart recorder to its terminals and use a ring stand to support the pile with the junctions facing down. One set of junctions should be thermally insulated to maintain a uniform reference temperature. The other junctions will be used as the measuring junctions. The recorder should be set on standby except during actual runs, the speed should be about 1 cm./min. and the sensitivity set using the match flame on one junction to give slightly less than full scale deflection. Using an ice salt mixture and a process similar to experiment 20, record the temperature on the chart every 5o-10o. Repeat the above process 2-3 times, gently bending and insulating a different number of measuring junctions each time. Finally, determine the temperature of a match flame by insulating all but one of the junctions, heating this one and extrapolating the results of your previous graphs.

References: S&Z 285, M 460


EXPERIMENT 24 - THE MECHANICAL EQUIVALENT OF HEAT

It is most convenient if you perform this experiment in the dark room. Use the heating coil supplied, insert two thermometers in the stoppers and connect the sink drain, one of the other tubes goes on the water faucet and the third one goes to the heating coil. A short hose with clamp then goes from the other end of the heating coil to the sink. In order to avoid the fountain effect requiring a large amount of cleaning up, turn the water on slowly, allowing water to flow out through the overflow and coil. The overflow will probably gurgle. The flow of water through the coil should be adjusted by moving the coil's outlet tube or readjusting the clamp. The flow will probably be very small but some flow must be present at all times. Using the D.C. power supply, the electrical terminals are hooked up as follows: one end of the coil directly to one of the terminals, the other end to the ammeter, then from the other end of the ammeter to the other D.C. terminal. Use the 10 amp scale. The voltmeter should be connected directly across the coil using the 5 volt scale. In order to avoid damage to the equipment and the wrath of the instructor, the proper polarity on the meters must be used and the hookup should be checked before the electricity is turned on. If more than one ammeter is supplied, hook them up in series and average their readings. Obtain a reading of somewhat over 6 amps and adjust the water flow to obtain a temperature difference of 3-10Co across the coil. Note: There must always be some water flowing from both the overflow and the coil drain. Make several trials at different currents and water flow rates. The mechanical equivalent of heat can be determined by measuring the quantity of water heated in a given time, the heat output and the work input. Do not leave the current on any longer than necessary since the power supply gets quite hot.

References: IIT lm 82, H&R 554, S&Z 306, M 288, S 130


EXPERIMENT 25 - THE CONSTANT VOLUME GAS THERMOMETER

Using the idea that the pressure of a gas is directly proportional to the kelvin temperature of the gas provided the volume is constant (an idea you will derive), plot and explain the shape of a cooling curve of a beaker of hot water exposed to room temperature vs. time. To obtain the curve, boil water with the closed flask in it and, with the water still boiling, hook the tube from the flask to one side of the manometer, then shut off the heat. You should use the atmospheric pressure as your standard and the boiling point of water at that pressure (in degrees Kelvin) and keep the volume of the confined gas constant by raising or lowering the open arm of the manometer to keep the closed atmospheric pressure reading should be taken at specific, uniform time intervals, possibly every minute or two. It is possible to obtain a computer printout for the results. Explain the graph and your results.

References: H&R 529, M 282


EXPERIMENT 26 ELECTRIC FIELD NEAR SEVERAL CHARGE DISTRIBUTIONS

Using the two boards supplied with this experiment, you are to experimentally determine equipotential surfaces and, from these, draw the electric field lines. For this experiment, use the board with only two bolts and the board with only one bolt and a COMPLETE border. The black paper on these boards is a conducting paper which is expensive and can be damaged if handled roughly. Connect the center bolt of the single bolt board to the + (red) terminal on the small green power supply and the border to the - (black) terminal. Plug in and turn on the VTVM (set to the 15 volt DC scale) and then connect the black (gnd) lead to the black wire attached to the border. Then, using the other VTVM lead as a probe, find enough points at some single potential to enable you to get a good idea of what this 'surface' is shaped like. Repeat this for at least three other potentials. It might be easier if you just transfer the coordinates onto graph paper directly from the board, using different colors to represent the different potentials. When you have done this for the board with a single bolt and complete border, then do the same thing for the board with the two bolts, only connect the + lead to one bolt and the -to the other. From these equipotentials, construct the field lines and indicate whether they look like what you expected (or what the book predicted). Note: you will be sharing the power supply with the group performing experiment 27, so set it up someplace convenient to both groups.

References: H&R 670, S&Z 387, M 364, S 136


EXPERIMENT 27 ELECTRIC FIELD NEAR SEVERAL CHARGE DISTRIBUTIONS

Following the same general procedure as that of experiment 26, plot the equipotentials and field lines of the following charge distributions: 1) Use the board with four bolts and connect three of the bolts to the + on the power supply and the remaining one to the -. 2) For this trial, use the board with one bolt and a border on ONLY ONE side, connecting the + from the power supply to this bolt and the - to border. In both experiment 26 and 27, how do your plots compare with the theoretically predicted plots? If there are any major differences, explain them.

References: H&R 670, S&Z 387, M 364, S 136


EXPERIMENT 28 - THE CHARGE ON THE ELECTRON

With the help of several pieces of equipment, the charge on the electron may be found. You will need the D.C. power supply, a graduated cylinder, clamp, tongs, timer, ammeter, platinum electrodes, sulfuric acid and container. WARNING!!! ---- The acid is very corrosive, if any acid enters the electrodes, gets on skin or clothing, promptly wash it in cold water as the acid will eat holes in whatever it is on. Connect the power supply, through the ammeter, to the electrodes and submerge the platinum ends in the acid, the polarity on the ammeter must be observed and the bent electrode hooked to the negative side of the power supply. Why? Adjust the current to some convenient value (no more than 4 amps) and watch the ammeter and try to keep the current constant throughout each trial. By filling the graduated cylinder such that its mouth is under the surface of the acid and pulling out the stopper with the tongs, you should get a water filled column. Mount this securely with the clamp and support. Measure the time necessary for collection of the given amount of gas from the negative electrode. The surface of the acid and the water inside the cylinder must be at the same level at the end of each trial so that you know that you have atmospheric pressure inside. By correcting this volume (in liters) to STP, you can find the number of molecules collected (n). There are two electrons collected per molecule so you can determine the charge of an electron by using e-=Q/2n where Q is the total charge, which is obtained by multiplying the current times the time. Make several trials and average your results. How much error would have been introduced if you failed to correct to STP?

Reference: H&R 654, S&Z 405, M 568, S 136

* * * * * * * * * * * * * * * * * * * *

!!!! C A U T I O N !!!!* * * *!!!! W A R N I N G !!!!

READ THIS PARAGRAPH!


The voltages and currents you will be using in some of the following experiments are dangerous!!!! DO NOT touch anything until you are sure of what you are doing. It is very good practice to keep one hand behind your back or in your pocket and to remove your rings and watch. You must NOT attempt to help or give advice or even approach a group if they are using high voltages. For the experiments using cathode ray tubes, you MUST wear safety goggles. A long sleeved shirt or sweater should also be worn. Experiments 30, 32, 33 & 34 will all use the same power supply, therefore, once your equipment is hooked up and checked, you should wait until the other groups are also hooked up and checked as there will be a change in voltage whenever a tube is turned off. Whenever you connect or disconnect your equipment, the high voltage must be turned off. If you do this while other groups are working on an experiment, warn them, then, when you are finished with the wiring, reset the voltage back to where it was.


EXPERIMENT 29 - THE ELECTRIC DING-DONG

See Caution. In this experiment you will be using the 10,000 volt power supply, the two plates on tripods and the conducting ping pong ball. Hang the ball between the two plates from one of the hooks over the front table. The plates should be placed parallel to each other about 4-5 cm. (plus the diameter of the ball) apart. Attach one lead from the power supply to each plate. Turn on the power supply and increase the voltage until the ball starts to swing, producing a chiming. Note: It may be necessary to start the ball by gently pushing on the string, not the ball (the ball is charged when it is between the plates). When not taking readings, turn the power supply down to zero, especially when doing anything near the plates. You should have the plates just far enough apart so that the ball barely touches them and does not bounce. The period of oscillation can then be found by timing with a stopwatch. This is your experimental value. Knowing the mass of the ball, its radius, the plate separation and the voltage, you can, by applying Coloumb's law, Newton's laws and various other equations, determine the theoretical period.

References: Most of the above


EXPERIMENT 30 - THE CATHODE RAY TUBE

See caution. By using the power supply, the control boxes and connecting cables provided, you are to calibrate a cathode ray tube. Plug in the wires, cables, control box and a 3BP1 tube (the number is on the tube, the first digit is the size, in this case, a 3" tube). The neck of the tube should light faintly. By increasing the voltage to about 500, a green spot should appear on the screen. By turning the intensity and focus controls, you should note and write up the effects of each on the spot. Use the portable power supply to apply a D.C. voltage to one set of plates, measuring the deflection of the spot and plotting the voltage vs. deflection for both + and - voltages. Do the same for the other set of plates. Were your results exactly the same? Why? Now use one A.C. voltage and explain any variations observed between the deflection voltage as obtained from your previous graphs and that read from an A.C. voltmeter (not the meter on the power supply). Repeat your measurements for a 5BP1 and a 7JP4 tube. The group performing this experiment is responsible for setting up and putting away the power supply and cables for everyone using them.

References: S&Z 491


EXPERIMENT 31 - THE POTENTIOMETER

You will need the potentiometer, a galvonometer, the resistor string, the 10 volt cell, a standard cell, the VOM and the VTVM. Plug in and turn on the VTVM so it can be warming up. Using the VOM and the VTVM and the circuit in figure 1, measure the voltage across each of the resistors in the string as per instructions with the string. Using the standard cell, calibrate the pot such that the galvonometer reads zero with the pot set on the voltage given for the standard (see figure 2). Again measure the resistor voltages with the pot (see figure 3) being careful when connecting it so as not to damage the galvonometer, possibly taking as an initial value that found with the VTVM. Explain the large differences observed.

References: H&R 801, S&Z 467, M 411, S 163


EXPERIMENT 32 - THE CHARGE TO MASS RATIO OF THE ELECTRON

See caution. The equipment you will use is the 3BP1 cathode ray tube and associated components (see experiment 30 for the approximate set up) plus the 3" solenoid. Note: You will be sharing the power supply with other groups, therefore run your power lead from the supply, leaving the supply in a central location. With the tube approximately centered and level in the solenoid, obtain a green spot, rotate the apparatus or arrange a bar magnet such that the spot is centered on the face of the tube, then defocus the spot. By running current through the solenoid, you should notice that the spot refocuses. By knowing the accelerating potential (V), the distance between the screen and the anode (L), the current through the solenoid needed to refocus the spot (i), the dimensions of the solenoid (L') and the number of turns on the solenoid (N), you will clearly derive and use the equation to determine e/m (=(8pV)/(B2L2) where B=loNi/L' Note: L]L'). The accelerating potential is the voltage on the tube's power supply, not the voltage on the power supply connected to the solenoid. Do two trials, with the second trial finding the next higher focusing current (remember to divide this by two since the electrons have completed two complete spirals inside the tube).

References: H&R 835, S&Z 486, M 570, S 175


EXPERIMENT 33 - THE CHARGE TO MASS RATIO OF THE ELECTRON

See caution. Follow the procedure outlined in experiment 32, only use the 5BP1 tube, 5" solenoid and, instead of finding the second focusing point, do one trial using only one coil and a second using both coils in SERIES. What additional inaccuracies are introduced using this setup as compared with that of experiment 32?

References: H&R 835, S&Z 486, M 570, S 175


EXPERIMENT 34 - DIP ANGLE AND STRENGTH OF EARTH'S MAGNETISM

See caution. Using the 7JP4 tube and hookup as in experiment 30, orient the tube in a north-south direction and mark the spot on the tube face, then, using the wooden holder and, without rotating the tube, flip it completely over (180o) along a vertical plane. You should notice that the spot has moved to the other side of the screen. Draw a line between these two points. Now, carefully hold the tube vertically and mark the position of the spot on either side of the line previously drawn (you will need to rotate the tube along the vertical axis). The ratio of the length of the line to the distance between the second set of points is the tangent of the dip angle (prove it). Also, using the distance between the second set of dots, you can determine the radius of the arc of the circle described as the electrons travel the length of the tube. (R=L2/D, where L is the distance from the second anode to the face of the tube.) By knowing the accelerating voltage you can calculate the velocity of the electrons and, once you derive the proper equations, you should be able to find the horizontal intensity of the earth's magnetic field. You will probably need to use e/m in your equations.

References: IIT lm 145, S&Z 543, M 436


EXPERIMENT 35 - DETERMINING THE INDUCTANCE OF SEVERAL COILS

By using the bridge circuit in figure 4, you will determine the inductances of several coils. Using the VTVM, determine the D.C. resistance of the coils by taking resistance readings on two different scales and average these two readings. Two conditions must be met in the circuit in order to produce a null (as straight a line as possible) on the oscilloscope. First, the wheatstone condition must hold. (What is the wheatstone condition?) Second, the inductive reactances must cancel (what is inductive reactance?) which means that Lx = Ls(R1/R2). Both conditions are mutually independent (why?) but must be met simultaneously. When adjusting the resistance boxes, you will notice that a null cannot be achieved by changing only one resistance but that the display will pass through a minimum. When this happens, try adjusting one of the other boxes until it also produces a minimum. Continue in this manner until each box has been checked several times and they are all producing the best minimum. There is no error analysis necessary but Rx should be determined from the wheatstone condition. Make note of Lx for each coil as you will need this information for experiment 37.

References: IIT lm 164, H&R 870, S&Z 579, S 190


EXPERIMENT 36 - CAPACITOR DISCHARGE

Using the single capacitor with its shunt (resistor in parallel across the terminals), the chart recorder and portable power supply, you will determine the capacitance of this capacitor. Turn on the chart recorder (DO NOT turn it off until you are done with the experiment) and connect the two wires coming from the sens board to the terminals on the back of the recorder (red to red, black to black) and the two terminals on the sens board to the terminals on the capacitor (CAUTION: ALWAYS connect red to + on a capacitor). Turn on the servo and, with the sens turned to zero, set the pen to zero using the zero adjust control. Connect the power supply to the capacitor (+ to red) and charge the capacitor by turning the power supply voltage about half way up. Leaving the power supply as is, adjust the sens control to produce a pen deflection slightly less than full scale and, by using the power supply voltage, slowly move the pen slightly off of the top end of the scale. Start the chart running at some suitable speed and disconnect the power supply (then, AFTER you disconnect the power supply, turn it down to zero). The chart should then begin to record the graph of a negative exponential. When this graph falls below 5-10, you may stop. Repeat the entire experiment with the large capacitor string. (NOTE: with the large string, you will probably be able to let the graph run for 40-50 minutes so use a suitably slow chart speed. At least one member of the lab group must be present to monitor the equipment throughout the entire experiment.) From these two graphs, plot graphs of ln (base e logarithm) of V/Vo vs. time (it should be a straight line). The slope of this line is -1/RC where R is the shunt resistance and C is the capacitance. You should derive this equation. Calculate C from your graph. Also find C from the time constant of the circuit (as found from the graph). Since the recorder and the resistors are 1%, your error should be less than 2%. Unfortunately, the values marked on the capacitors are 100% so no error analysis is possible except that your values will be compared to the values found on a precision instrument. You should, however, find the percent difference each of your values is from the actual values as marked on the capacitors.

References: H&R 802, S&Z 589, S 179, QC 42&172


EXPERIMENT 37 - THE MUTUAL INDUCTANCE BETWEEN TWO COILS

Using the two coils whose inductance you found in experiment 35, and the same bridge arrangement, you will attempt to measure their mutual inductance (what's that?). Put the two coils in series, in place of the single unknown coil of experiment 35 and set one on top of the other. By determining the inductance of this combination, flipping one of the coils over and determining it again, you will find that you have two different values. This is because the total inductance is given by Lt=L1+L22M, where M is the mutual inductance you are trying to find. In one configuration, you were using the + and in the other, the -. Determine M for each trial. Do these two values fall mutually within the error predicted?

References: IIT lm 164, H&R 870, S&Z 397, S 190


EXPERIMENT 38 - LC RESONANCE

Before you come to class, look up and determine the conditions for A.C. resonance in an LC circuit. Hook the audio oscillator, the 30 ohm resistor, the 1 lfd capacitor and the small inductance coil in series. See figure 5. Follow the instructions on the back of the circuit board for connecting the chart recorder or see experiment 36 for the initial setup on the recorder. Turn on the oscillator, chart recorder and VTVM and allow them to warm up. Hook the VTVM across the oscillator. Calculate the resonance frequency of the circuit (if you haven't already run a computer plot) and set the oscillator for this frequency. Using the 5 volt A.C. scale on the VTVM, adjust the oscillator's output to 2 volts. Adjust the sens control on the chart recorder for a deflection of about 70. Now slowly vary the frequency 20-30hz. to either side of this resonance point and if the recorder goes up, readjust the sens and voltage until you get back to the original deflection. The circuit must be allowed to stabilize for at least 10 seconds after each frequency change. Select some chart speed and timing interval which will allow you to produce a graph which is about the same length and frequency range as your computer plot. After each frequency change, quickly reset the output level on the oscillator back to 2 volts. Every 50hz or so, mark the frequency on your chart for reference. Draw a SMOOTH curve through this set of points and compare your results from each graph and explain any differences. Turn in both plots.

References:H&R 952, S&Z 600, M 478, S 198


EXPERIMENT 39 - MELDE'S EXPERIMENT

See exercise 39 (the sheets with the experiment). You may duplicate these sheets but do not write on them or take them with you as other groups will need them. Your equipment consists of a string attached between a motor and a mounted pulley. You should clamp the motor and pulley to the tables as far apart as the string will allow, with 10-15cm extending beyond the pulley. DO NOT remove or readjust anything on the motor mount or drive. Using the can provided, add sand until a resonance point is found. This can be precisely reached by noting that, when the resonance point is reached, the can will rise and not drop back down. The total weight of the can, sand and string hanging from the pulley is the tension in the string. While you are doing the three or four segment part, you should also determine the actual speed of the motor using the attached revolution counter and a stopwatch. You should perform the error analysis found on the exercise sheets and answer the questions proposed.

References:IIT lm 99, H&R 463, S&Z 234, M 227, S 202


EXPERIMENT 40 - THE SPEED OF SOUND

With the circuit and equipment described in figure 7, determine the velocity of sound for the particular day you are performing this experiment. You should get two Lissajou figures on the scope. If you don't know what a Lissajou figure is, it would be helpful if you did a little research before coming to class. By adjusting the audio oscillator to 2500hz, you should get a 5-1 pattern. By moving the microphone towards or away from the speaker, you should be able to count the number of complete rotations that the 1-1 pattern makes and, from this, determine the wavelength. Do this as many times as possible for as many rotations as possible until your data looks consistent. Average these numbers. Then, from the wave equation, calculate the actual speed of sound. Compare your results to those obtained from an equation taking into account the atmospheric pressure and temperature on the day you did the experiment. Note: The audio oscillator will be producing 2500hz with less than 1hz error if your 5-1 figure is rotating less than once per second, which means you can achieve four place accuracy. Why do both patterns rotate when the microphone is moved?

References: IIT lm 98(#3), H&R 500, S&Z 246, M 221, S 204


EXPERIMENT 41 - GUESS WHAT

You are to create an experiment. The experiment can be in any area of physics and can be taken from any lab manual except this one and the one you used in your first year, provided the equipment is available, the experiment is good physics and can be done in 84 minutes. A finalized, brief outline listing the type of experiment, approximate procedure to be followed and the equipment needed must be submitted at least four school days before you plan on performing this experiment. It is suggested that you submit your outline as early as possible just in case some minor points need changing: i.e., new experiment, being too dangerous, not good enough or to give your instructor time to leave town.

References: Any or all of the above plus some.


EXPERIMENT 42 - READING THE SCALES ON A PRISM SPECTROMETER

You will be determining the apex angle of a prism and also learning to read the vernier scales on a prism spectrometer. The prism should be mounted such that the apex angle is in the center of the stage and splitting the beam, with one segment reflecting off of each of the two adjacent sides. Take a reading on one side, swing the telescope around (do not move the stage) and take a second reading through the same window. By subtracting the two readings, you can find the total angle, which is twice the apex angle (prove it). Your total angle should be 120o5o and if it is radically off, you may have gone past the 360o mark, you should check this. The outer scale reads in half degrees (30 min) and the vernier scale reads in one minute divisions. The angle in degrees and 30 minutes is read to the left of the zero on the vernier, then to get minutes, you find the vernier line that is aligned with any line on the main scale and read the number off of the vernier, adding this to your previous reading off of the main scale. It would be best if each member of your group read the angle and you then had the instructor read it also, comparing these values (readings within about 2-3 minutes should be achieved). If you have time you may want to start (and maybe finish) experiment 46.

References: IIT lm 117


EXPERIMENT 43 - THE WAVELENGTH OF SODIUM LIGHT

Using the precision Michaelson interferometer and the sodium vapor light source, you will determine the wavelength of yellow sodium light. Set up and align the interferometer such that the fringes are visible. This may take some time and playing with, but DO NOT touch the mirrors. Once fringes are found, you should notice that, by turning the screw handle, the fringes move. You should then take a reading and continue to turn it in the same direction, counting at least 100 fringes. This will give you a distance reading for a given number of wavelengths. Turn the screw in the opposite direction until the fringes start to move and again count them and take a distance reading. You should notice that, unless you continue in the same direction, you cannot use the ending reading as the start of the next trial. Do this as many times as your eyes will allow and average your results. It would probably be best if you alternate with your lab partners so as to remain sort of sane (?) after watching and counting the fringes several times. You may observe that, at some positions, the fringes disappear. If this occurs, adjust the micrometer screw to another position a centimeter or two away and start the reading over. Each member of the lab group should do at least one trial to spread the misery around. The ratio of measurement to table movement is 25:1 on the gray interferometer and 50:1 on the brown one. When you are finished, be sure to COVER the MIRRORS.

Reference: IIT lm 136


EXPERIMENT 44 - THE WAVELENGTH OF LIGHT

You should calibrate the center row of gratings on the diffraction grating slides using the laser (wavelength=6328P). Mount the grating on the front of the laser and project the pattern the length of the room. Using the proper equation, you can find the slit spacing. Find the angle by measuring the spot spacing and the distance from the grating to the spots. The beam should hit the wall as nearly perpendicular as possible. How much error is there in your value? After you have calibrated your gratings, use a 2-meter meterstick, a line filament lamp and several filters and determine the average wavelength for each filter, comparing your values with those given in a reference for approximately the same color as that of the filter used. Use caution when using the laser so that it does not accidentally shine into someone's eyes.

References: IIT lm 125, H&R 1123, S&Z 672, M 524, S 233


EXPERIMENT 45 - THE INDEX OF REFRACTION OF AIR AND GAS

Using the cheap interferometer, you are to find the index of refraction of air. You must pump the system for at least one minute after the pump stops squeaking to insure a reasonably good vacuum. Take several readings and compare your calculated values with the actual value. Note: Since you are adding 1 to your value, you should subtract 1 from both the book value and your value before finding the error. Try several more trials using gas from the table jets. Hook up the bunsen burner and let it burn for several minutes to bleed all of the air from the system. Pump the chamber full of a vacuum, with the vacuum sealed in, turn on the gas and hook the tube from the gas jet to the valve and then complete this part the same way that you did with air.

References: IIT lm 114, H&R 1014, S&Z 614, M 496, S 219


EXPERIMENT 46 - PRISM SPECTROMETER AND CAUCHY COEFFICIENTS

With the prism spectrometer used in experiment 42, you will set up equations and find the angles of minimum deviation for four prominent spectral lines of mercury. It is your responsibility to find out how to find the angles of minimum deviation before you come to class. When this has been done, take three of the wavelengths, their corresponding angles and the apex angle and feed this data into the computer program supplied. You should derive the equations used and explain the meaning of Cauchy's coefficients. You should then take the fourth wavelength and substitute it into the equations to check your derived results.

References: IIT lm 117, H&R 1032, S&Z 626, M 560, S 219


EXPERIMENT 47 - PHOTO EMISSION AND CONDUCTION

A plot of the conductivity of a photo-cell vs. wavelength of light will be made and, you hope, explained. Connect the arc-lamp on the side table so that it projects a spectrum along the surface of the lab tables. On the other side of the room, set up the cell on a board and paper tape such that it can be drawn through the spectrum by the drive motor supplied. Wire the recorder as in figure 6, with the chart speed set at 10cm/min. The lens on the arc lamp must be cleaned after each use. When everything is ready, strike the arc (gently). This is done by gently turning the black knob on top of the arc- lamp until the rods touch, then backing it off until a bright arc is obtained. It should emit a faint, fairly constant buzzz, if it doesn't, try readjusting it. This must be done by feel as you must not look into the arc. Do not leave the arc on more than necessary as it gets quite hot and the lens clouds up. By pulling out the silver knob on the end of the lamp, it should start ticking, this is the automatic feed and will help keep the arc constant and blow up the experiment if it is not done correctly. Mark on the plot the colors as the cell passes each one and explain this plot.

References: H&R 1179, S&Z 724, M 571, S 237


EXPERIMENT 48 - THE SIZE OF A MOLECULE

Determine the size of a molecule and attempt to verify Avagadro's number. It works best if a uniform, thin layer of powder is used.

References: Modern Physics Workbook l964 pgs 43&44, S&Z 350


EXPERIMENT 49 - BRAGG DIFFRACTION

Using the microwave equipment, you will determine the molecular spacing in the simulated crystalline structure. Determine the wavelength of the projector by setting up standing waves between the projector and a metal sheet about 1 meter away. A diode detector is then hooked to the audio amplifier and the wavelength measured by moving the detector along the beam, near the metal sheet, measuring the distance between several nodes. (Why?) Once you know the wavelength of the beam, you can use the principles of Bragg diffraction to determine the molecular spacing. You must look up and determine the conditions required in order to perform this experiment before you come to class. Use the meter as your detector in the second part, the clear plastic side is the receiver. Describe the similarities between this method and one using X-ray diffraction, what advantages does each posses? Hint: n may be any integral number between 0.1 and 10 and should be chosen to produce a spacing with some nice value.

References: H&R 1140, S&Z 800


EXPERIMENT 50 - RADIOACTIVE DECAY

With cubes as simulated molecules, you will attempt to verify some of the principles of radioactive decay. Starting with a 'no-hole' side, throw the cubes onto a suitable surface and remove every cube whose selected side is on top. It may be necessary to carefully move some of the cubes so they are not stacked on top of each other. Do this again, continuing to throw and remove them as fast as possible until less than 6 are left, keeping track of how many are left after each throw. Repeat this entire process at least twice for the same side. Plot the total number left for all trials vs. the throw number. You should remember that this curve should be a smooth curve and does not need to go through every point, just close. During the second 40 minute period, do the same but start with a 'hole' side. How does this experiment compare with one measuring normal radioactivity with geiger counters and other electronic equipment? In each trial, determine the 'half-life' of your cubes in terms of throws and, from this, find the decay constant, comparing this number with the probability of an individual cube 'decaying'.

References: H&R 196, S&Z 869, M 19, S 242


NASTY COMMENT



Well, if you survived this far, you will probably live through most any type of lab course. Think now, are you still sane? If so, well, at least I tried.






BIBLIOGRAPHY



     NOVEL EXPERIMENTS IN PHYSICS   American Institute of Physics

                                                             1964



     THE HANDBOOK OF PHYSICS AND CHEMISTRY     CRC publishing Co.

                                                       1929, 1964



     THE PHYSICS TEACHER            American Institute of Physics

                                                       April 1968



     Becker                 INTRODUCTION TO THEORETICAL MECHANICS

        McGraw Hill Publishing Co.                           1954



     Cleveland et. al.      IIT GENERAL PHYSICS LABORATORY MANUAL

       Edwards Brothers, Inc.                                1957



     Williams et. al.                              MODERN PHYSICS

       Holt, Rinehart and Winston Inc.                       1968



     Williams et. al.                     MODERN PHYSICS WORKBOOK

       Holt, Rinehart and Winston Inc.                       1968



     Halliday & Resnick                        PHYSICS PARTS I&II

       Addison-Wesley Publishing  Co.                        1966



     Holton & Roller       FOUNDATIONS OF MODERN PHYSICAL SCIENCE

       Addison-Wesley Publishing Co.                         1958



     Kleppner & Ramsey                             QUICK CALCULUS

       John Wiley & Sons Inc.                                1965



     McCracken                  A GUIDE TO FORTRAN IV PROGRAMMING

       John Wiley & Sons Inc.                                1965



     Miller                                       COLLEGE PHYSICS

       Harcourt, Brace & World                               1967



     Richards et, al.                      MODERN COLLEGE PHYSICS

       Addison-Wesley Publishing Co.                         1962



     Schaumn                           OUTLINE OF COLLEGE PHYSICS

       McGraw-Hill                                           1961



     Taffel et. al.                     PHYSICS LABORATORY MANUAL

       Allyn & Bacon                                         1966



     Watson                                   TEXTBOOK OF PHYSICS

       Longmans, Green & Co.                                 1899  



ADDITIONAL REFERENCES



     EXPERIMENT                 REFERENCES

        1       IIT lm 22, H&R 48, S&Z 62, M 35, S 27, QC 138

        2       IIT lm 47, H&R 48&140, S&Z 62&229, M 35&195, S 27&84

        3       IIT lm 41, H&R 219, S&Z 167, S 63

        4       H&R 59, S&Z 104, M 44, S 31

        5       IIT lm 22, H&R 101, M 66, S 41

        6       IIT lm 32, H&R 345, S&Z 218, M 187, S 183, QC 272

        7       IIT lm 25, H&R 85, S&Z 83, M 58, S 35, QC 138

        8       QC 9&38

        9       IIT lm 109, H&R 118, S&Z 117

       10       S 43

       11       H&R 66, S&Z 112, M 155, S 71

       12       H&R 458 (Problem 9), S&Z 207, M 260, S 94

       13       IIT lm 36, H&R 320, S&Z 20, M 86, S 1, QC 25

       14       IIT lm 36, H&R 320, S&Z 20, M 86, S 1, QC 25

       15       IIT lm 27&45, H&R 286, S&Z 179&183, M 156&165, S 67&75

       16       IIT lm 27&45, H&R 286, S&Z 179&183, M 156&165, S 67&75

       17       IIT lm 27&45, H&R 286, S&Z 179&183, M 156&165, S 67&75

       18       IIT lm 27&45, H&R 286, S&Z 179&183&195, M 156&165&179, S 67&75

       19       H&R 433&572, S&Z 350, M 305, S 114

       20       M 317, S 114

       21       IIT lm 88, S&Z 310, M 292, S 124

       22       IIT lm 86, H&R 563, S&Z 310, M 292, S 124

       23       S&Z 285, M 460

       24       IIT lm 82, H&R 554, S&Z 306, M 288, S 130

       25       H&R 529, M 282

       26       H&R 670, S&Z 387, M 364, S 136

       27       H&R 670, S&Z 387, M 364, S 136

       28       H&R 654, S&Z 405, M 568, S 136

       29       Most of the above

       30       S&Z 491

       31       H&R 801, S&Z 467, M 411, S 163

       32       H&R 835, S&Z 486, M 570, S 175

       33       H&R 835, S&Z 486, M 570, S 175

       34       IIT lm 145, S&Z 543, M 436

       35       IIT lm 164, H&R 870, S&Z 597, S 190

       36       IIT lm 160, H&R 802, S&Z 589, S 197, QC 42&172

       37       IIT lm 164, H&R 870, S&Z 597, S 190

       38       H&R 952, S&Z 600, M 478, S 198

       39       IIT lm 99, H&R 463, S&Z 234, M 227, S 202

       40       IIT lm 98 (rep. 3), H&R 500, S&Z 246, M 221, S 204

       41       Any or all of the above plus some

       42       IIT lm 117

       43       IIT lm 136

       44       IIT lm 125, H&R 1123, S&Z 672, M 524, S 233

       45       IIT lm 114, H&R 1014, S&Z 614, M 496, S 219

       46       IIT lm 117, H&R 1032, S&Z 626, M 560, S 219

       47       H&R 1179, S&Z 724, M 571, S 237

       48       S&Z 350

       49       H&R 1140, S&Z 800

       50       H&R 196, S&Z 879, M 19, S 242



    The following abbreviations are used in the above list: IIT lm-Illinois

      Institute of Technology General Physics Laboratory Manual 1956;

      H&R-Halliday and Resnick 1966 (dark blue); S&Z-Richards, Sears, Wehr &

      Zemansky 1962 (gray); M-Miller 1967 (green); S-Schaumns 6th ed.;

      QC-Quick Calculus 1965


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