A Switch That Flips Another Switch

A Switch That Flips Another Switch

Name Date
DIRECTIONS: Read how a switch can flip a switch, then trace the chains overleaf.
1Read how a switch flips a switch
→
2Turn over: trace the chains
worked by a fingertwo ends. Something alive has to touch it.worked by electricityinoutflipthree ends. Nothing has to touch it.that third wire is where computers come from

A finger switch has two ends, and someone has to press it.

Give it a third wire, so current in that wire closes it. The oldest kind is a relay: the third wire is a coil that turns into a magnet and pulls an iron arm across. The first computers used thousands.

What just happened

The thing that flips the switch is now the same kind of thing that comes out of one: electricity. So one switch’s out can work the next one’s flip, in as long a chain as you like, with no finger anywhere. The rest of this pack is this one idea, stacked.

A transistor is the same thing with nothing moving inside: in, out, and a third wire that decides. With nothing to move, it can flip billions of times a second.

Follow the Signal

A Switch That Flips Another Switch

DIRECTIONS: Trace each chain with a finger, one switch at a time. Write ON or OFF.
inswitch 1switch 2inswitch 3inlampnobody is touching any of it

Now a chain that flips

A flipper is built the other way round. Current in, nothing out. Nothing in, current out.

Goes inHow many flippersComes out
ON2Done for you OFF, ON → ON
ON3
OFF4
ON5

Look at your answers. What about the number of flippers decides what comes out? Use it on a chain of a hundred.

Two more things a wire can do

to another switchto another switchto another switchone output, three inputs — this is why a machine can grow

One out, many flips. Split a wire and one output works three switches at once.

Backwards. What if a switch’s output ran back to the flip wire of one before it? Have a think. Sheet 40 has the answer.