Elenco Electronics 202 - Manual (Page 106)

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Project #249
OBJECTIVE: To learn about the electromagnet.
Electromagnet
Delayer
Build the circuit and turn it on. After a delay of about 2 seconds, the
lamp (L2) will light but be dim. Replace your batteries if it does not light
at all.
Why does the electromagnet (M3) delay the lamp turn-on? The
electromagnet contains a large coil of wire, and the batteries (B1) have
to fill the coil with electricity before the lamp can turn on. This is like
using a long hose to water your garden - when you turn on the water it
takes a few seconds before water comes out the other end.
Once the lamp is on, the resistance of the wire in the coil keeps the
lamp from getting bright.
Project #250
OBJECTIVE: To show how electricity can lift things using
magnetism.
Photoresistor Paper
Clip Suspension
Take a paper clip and straighten it out, bend it in half, and place it into
the electromagnet (M3) center. Turn on the slide switch (S1), the paper
clip gets sucked into the center of the electromagnet and stays
suspended there.
Now move the adjustable resistor (RV) control lever around while
waving your hand over the photoresistor (RP). Depending on the
adjustable resistor setting, sometimes covering the photoresistor
causes the paper clip to fall and sometimes it doesn’t. You can also
adjust the light to set the paper clip to different heights.
Drop in
Straighten and bend paper clip