**The Millikan L'Eggs Experiment**

Coleman, Roy Morgan Park High School

881-5050

**Objective:**
To use discrete masses to simulate the Millikan experiment (the
discrete charge on the electron).
**Apparatus:**
one balance per group and EITHER
a large number of L'Eggs eggs (from panty-hose) individually numbered
and filled with ball bearings or clay such that the filler is
divided into 'unit masses' i.e. for a ball bearing filler, use
multiples of 7 bearings (or some multiple larger than the weight of
the 'shell'). It is nice to have several regular intervals and
then skip one (put in two additional unit masses)
OR
10 numbered plastic Easter eggs filled with clay or bearings (as with
the L'Eggs eggs) for each group
**Strategy:**
Present the problem of how to find the mass of a unit 'yoke' where
there is a shell and **at least** one 'yoke' in each egg. If the students

cannot come up with the idea to mass them on a balance, suggest it.

After they have massed their eggs, some may see a pattern but suggest

that they draw a histogram of their data (mass vs. number of eggs with

that mass (NOT egg number)). It should be obvious from the graph that

the masses fall into several groups. From the average mass of each

group, students should be able to see that the groups fall at regular

intervals and that these intervals correspond to each additional unit

mass (one more 'yoke').

**Discussion:**
A discussion should be held to talk about the number of digits of
accuracy needed in the measurements since the shells and unit masses
will each vary by some small amount. It is possible for the students
to become so involved with making accurate measurements that they miss
the pattern or waste too much time on the weighing.
After the experiment is done, a comparison should be made between this
experiment and Millikan's oil drop experiment where he found the unit
charge of the electron by looking for regular intervals (or discrete
units of charge).

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