Make a switch

A switch is a way to turn the electrical current off and on. The diagram for a switch is diagram 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.

an old-fashioned switch When the switch closes, it connects the wire on the right to the wire on the left

write in your journalWith 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.
Morse code for STOP THE TRAIN


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: check box 
Next:About electrical current