Data Sheet

B
1mA
Project 55
Magnetic Induction
The meter shows an electric current even though no batteries are used. By mov-
ing the magnet near the coil, you have induced (created) a current in the circuit.
You have made electricity from magnetism - an electric generator! This simple
concept is very important to our society. High pressure water from dams or steam
(often heated by burning oil or coal) spins large magnets in coils to produce much
of the electricity that runs our cities.
Project 56
Electromagnetic Induction
A
Build the circuit as shown. Assemble the build-your-
own electromagnet as per the instructions on page
5. Push the wire on the build-your-own electromagnet
to one side and insert its iron rod into the top of the
electromagnet (M3), as shown.
Push the press switch (S2) and watch the white LED
(D6) when you press or release the switch; you
should see a flash. The flash on the LED is easier to
see if you look directly into the LED and block the
light from the lamps with your hand. If you don’t see
any flash on the LED then you may need to push the
iron rod further into the M3 electromagnet.
Pull the iron rod out the M3 electromagnet. The LED
should no longer light when you press the switch, be-
cause the magnetic connection between the circuits
is broken now.
You can replace the build-your-own electromagnet
with the one made with the red jumper wire in project
52 (wind the red wire on one side of the rod), but it
will not work as well because it has less windings.
You can also replace the white LED with the meter
(M5, on the 1mA setting).
Notice that this only works when the magnetic field is
changing due to you pressing or releasing the switch.
If you keep the switch pressed the magnetic field is
constant, and no current is induced in the electro-
magnet to light the LED.
Note: The lamps (L4) are in the circuit to limit the cur-
rent through the build-your-own electromagnet. If you
replace one of the lamps with a 3-snap wire then the
LED may flash a little brighter, but you should only
press the switch briefly because pressing it makes a
short circuit and may activate the fuse (see project 9
for more details).
Build the circuit as shown. Place the iron core rod into the electromagnet (M3) and set the meter
(M5) to the 1mA scale.
A. Move the magnet left-right or up-down near the electromagnet. You may see the meter pointer
wiggle, which indicates a small current.
B. Place the magnet on the iron core rod and use it to move the rod up and down IN the electro-
magnet. The meter pointer should move or wiggle slightly, showing a current is produced.
Try removing the iron core rod from the electromagnet and see how the current is affected.
If you have a more powerful magnet in your home, use it in place of the Snap Circuits
®
STEM magnet.
A more powerful magnet will create a larger current and be easier to measure.
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