Elenco Snaptricity&reg - Manual (Page 60)

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Electromagnet Direction Project #50
Educational Corner:
Electric Paths
1A
1A
Airport metal detectors work by
detecting a magnetic field change using
electromagnets.
The direction of a magnetic field from a current flowing in a wire (or
coil of wire) depends on the direction of the electric current.
For more fun: with the press switch pushed, try lifting the iron core
rod out of the electromagnet with a paper clip.
Description
Push the press switch (S2). The meter shows a current is flowing
and the compass needle is attracted to the electromagnet.
Note: in some cases your M5 meter may not be sensitive enough to
measure the current. If your meter shows zero, switch to the 1mA
setting, then switch back (the 1mA scale prevents the compass from
working here).
Now flip both slide switches (to position C) and push the press switch
again. The meter shows no current (because electricity flows in the
other direction) and the other side of the compass needed is
attracted to the electromagnet (magnetic field is reversed). In some
cases you may need to hold the compass closer to the
electromagnet for the needle to change sides.
If you remove the iron core rod from the electromagnet, the compass
needle attraction will be much weaker.
Operation
Build the circuit shown. Place the iron core rod in the electromagnet (M3),
set the meter (M5) to the 1A scale, set the slide switches (S5) to position B.
Assembly