Electric and Magnetic Fields

Garrison, Earnest S.                 Schurz H.S.
                                     794-8120
                           
                          
Objectives:  

         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.