the electromagnet you made, with the large nail inside it
one battery holder and battery *
wires with alligator clip ends *
a bipolar light emitting diode (that turns green or red,
depending on how it is connected to two batteries).
Compare the behavior of these two circuits, where we will use
only a single battery (1.5 V):
In these diagrams, the switch just means that
we don't permanently connect the battery into the
circuit -- instead, just touch the battery wire to
the other parts, to see what happens when you give
the circuit a short jolt or a longer application of
the voltage. Nothing is supposed to happen in the
circuit at left -- the voltage is not big enough
to operate the LED (but we check, anyway).
The circuit at right is more interesting.
Compare what happens if you connect the battery for
a few seconds to what happens if you just quickly touch
the battery wire to the rest of the circuit.
Compare what happens if you remove the nail from the
A motor contains an electromagnet. See what happens
if you replace the electromagnet by the motor in the
circuit at right, above. There are two things to try:
just letting the motor run, or holding the motor shaft
so that it cannot turn, as you connect and disconnect the battery.