Electric and Magnetic Fields

Garrison, Earnest S. Schurz H.S.


To introduce the concepts of MAGNETIC AND ELECTRIC FIELDS to
the students via the use of phenomenas as magnetism and electric
current flows.

Apparatus needed: Large magnets(2), Nails, Metal rings, Several Coils of wire, Van De Graff generator, Ping-Pong Ball, Fishing line, Several metal objects. Recommended strategy: Set up a stand that has several nails that are attached to the table (tape them if possible).Above the nails place one of the large magnet at distance that will cause the nails to appear to float in air.At this point a discussion is held concerning the set up. Several pieces of materials can be placed in the space between the magnets and the nails to illustrate the their effects on the magnetic field, this should enhance the discussion of the properties of the magnetic field as most objects other than thick metal plates have little or no affect on the floating nails. The Van De Graff generator can be used to demonstrate the electric field. Suspend a ping-pong ball above the table (use a ring stand if necessary) that has been coated with a metallic paint. The space around the ball is normal before introducing the Van De Graff into space near the ping-pong ball(make sure that the ball can't touch the Van De Graff if swong in that direction). When the generator is turned on the ping-pong ball should swing close to the generator. A discussion should start concerning the space around the ball and generator. Afterwards a small fluorescent tube can be placed in the space near the generator in way that both ends of the tube are the same distance from the generator's surface (creating an equipotential along the tube). Now the tube should be turned slowly in a manner to place one end of the tube close to the generator and the other away from it. The effect of the light glowing should be food for considerable discussion about Electric fields and fields potentials. Using some clear plastic and wire (heavy gauge) an overhead projection device can be constructed to illustrate the connection between electric and magnetic fields. The plastic should be cut in the shape of a rectangle and a small hole should be drilled in the center of the plastic about the size the of a 12 gauge wire. Then place a strip of wire through the hole in the plastic so that it is perpendicular to the flat surface of the plastics sheet. I-----0 WIRE ----> I I _______________I _____________________ / I / PLASTIC -------> / / /____________________________________/ I I 0--------I The two ends of the wire should be attached to a circuit that contains a six volt motorcycle battery and a knife switch hooked - up in series. Now iron fillings should be liberally spread around the plastic sheet. When the switch is closed circles should form around the wire. It may help to tap the plastic sheet gently to help see the lines of force form. These lines are due to the magnetic field made by the current in the wire. This should provide food for much discussion about electric currents and their associated magnetic fields.
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