A switch is a way to turn the electrical current off and on. The
diagram for a switch is which is a picture of how it works: as drawn, the two
wires are not electrically connected and no current can flow
through the device; but if you bring the two ends together, the
wires are connected electrically. Some switches actually look
exactly like this inside.
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When the switch closes, it connects the wire on the right to the wire on the left |
With these hints, do the activity "Current #3 Make a
switch" in the manual.
Most of the electrical components that we have studied serve to
turn electrical energy into other forms: motion, light, or sound.
The current through the device provides the energy, and determines
what will happen. A switch is different: it lets us control the
circuit. It lets us put information into the system: stop, go, yes,
no! When it is too cold, the thermostat turns on the switch that
makes the furnace go. A century ago, the telegraph was a
revolutionary new means of communication which consisted of just a
switch and a circuit. Closing a switch in New York would cause a
light to blink in San Francisco; the pattern of blinks would encode
a message.
Still more interesting is to have a switch that can be turned on and off electrically. We could make one, with a motor and some wires, but transistors accomplish this with no moving parts. This allows one current to control another. Connect together a few hundred million of these, and you can make your own computer.
Check the box when you are
done:
Next:About electrical current