Copyright © University of Cambridge. All rights reserved.
In this problem a circuit has been set up. There are two switches
on the left, two logic gates in the middle and two bulbs on the
right.
Currently the gates are both set to XOR. They can be changed to any
of the following: AND, NAND, OR, NOR, XNOR. Any switch or gate can
be altered by clicking on the blue square in its top left hand
corner. If you are unsure about the meaning of the logic gates,
take a look at
Circuit
Maker
Can you set the gates so that the number of bulbs which are on is
the same as the number of switches which are on? In other words:
when both switches are off both
bulbs are off,
when either switch is on one bulb is on,
when both switches are on both bulbs are on.
Full Screen
Version
This text is usually replaced by the Flash movie.
Other circuits to try to
construct
Can you set the gates so that:
when both switches are on both
bulbs are on,
the rest of the time - both bulbs
are off;
when both switches are off both
bulbs are on,
the rest of the time - both bulbs
are off;
when both switches are off both
bulbs are off,
when one switch is on both bulbs
are on,
when both switches are on one bulb
is on.
Experiment further with the effects of the different settings to
create similar problems: choose a setting for the two gates,
describe clearly the effect of your circuit and challenge a partner
to figure out your settings.
If you liked this problem you may like to build your own circuit
boards with interesting properties using the
Circuit
Maker interactivity, or try the harder
Adding
Machine problem.