BACKGROUND:
Communication was made possible by a telegraph.
Sending information through a wire was big step forward in developing
our current communication system. Although the telegraph, as represented
in this lab, is not used as much as it was, its other uses such as the
transmission of documents (FAX machines) have invaded the business
market. The principle of the telegraph is still used, students just
don't realize the impact to our society
PROCEDURE:
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 Emphasize that
electromagnets are very important, as discussed in previous
activities. This lab gives students hands-on experience with an
electromagnet and knowledge about how it works.
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First, draw the following
diagram on the board to refresh student's memory of an
electromagnet.
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Use the model of the
telegraph to demonstrate how it works, especially if this material
was omitted in the PRE LAB. Go over how a telegraph was built and
try to communicate with students using the Morse code. Use simple
words.
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Following directions on the
lab sheet, students will make a switch using tacks, a paper clip,
and cardboard. They should then use the alligator clips, a bulb, a
bulb holder, battery, and switch to make a set up as shown in the
diagram. Press the bent metal switch down on the tack. Release it.
When the switch is pressed, the circuit is complete and the light
flashes on. When the switch is released, the circuit is broken;
the switch will spring up and away from the screw and the light
will go off.
-
Students can practice the
Morse code using this "mini" light telegraph. Make sure
students know that there is no electromagnet in this exercise. A
real telegraph can transmit information much farther than the
simple circuit light telegraph because of the electromagnet which
pulses a "sounder."
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