Chapter 12 Electromagnetic Induction
231
Project 12-2: Repulsion
Coil
You can demonstrate induction and trans-
former action by building the repulsion coil
shown.
Gather the parts listed in the table. Then,
assemble the project by following procedure
and using the schematic.
Procedure
1. Cut the plastic or fi ber ends, and glue them
to tubing to make a coil form 3″ in diameter
and 3 1/2″ long.
2. Wind 2 1/2 lb. of No. 22 magnet wire on
the coil form. Wrap the wire in even layers.
3. Cut welding rods (coat hangers, 16–18
gauge steel wire, or a large bolt) to 4 3/4″
lengths.
4. Tape the rods together or use epoxy
at both ends to hold the individual rods
together and form the core of the repulsion
coil.
5. Make a base to fi t your needs.
6. Mount the coil on the base with wood
screws.
7. Attach the white wire, black wire, switch,
and fuse holder to the coil. See the
schematic.
8. Attach the lamp cord to the fuse holder.
Practical Application 12-1:
Using a Current Clamp
One major problem with measuring current
is opening the circuit to insert a meter. In some
cases, this can be very dangerous. There is
another solution to measuring circuit current
that involves the principles of induction and
transformer action. A current clamp, also known
as a current probe can be placed over the wire.
All you have to do is squeeze the clamp, place it
over the wire and release.
The magnetic fi eld from the wire will cut
through the clamp. This induces a current that
travels through the leads, is measured, and
then is displayed on a digital readout. You can
measure current in the range of 0.1 A to 300 A
with this current clamp.
3” dia.
3 1/2”
Welding rod
core 4 3/4” long
Coil
Fuse
Switch
(Project by Perry Jossefi des)