Electric and Magnetic Fields
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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
Large magnets(2), Nails, Metal rings, Several Coils of wire,
Van De Graff generator, Ping-Pong Ball, Fishing line, Several metal
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.
WIRE ----> I
/ I /
PLASTIC -------> / /
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.