Clone of Circuit Maker
Why do this problem?
This problem gives the simplest introduction into logic gates and
circuits. Through experimentation with switches, students will
begin to see the structure of logic gates emerge without the need
for any detailed formalism. They will then see that logic gate
circuits can be constructed with more complicated behaviour.
Possible approach
Put the problem on to the board. Encourage students to read
the problem and decide what the circuit board means. Encourage
experimentation with combinations of off /off. At each stage,
encourage students to describe what they can see. How can this
sensibly be recorded?
Once students feel that they understand how a gate works they
should write a sentence describing the action of the gate. Do
others agree that this is a clear definition? How might is be
improved? Could we use it in the definition of the behaviour of the
other gates?
You might like to discuss with the class how the words 'and'
'or' and 'not' are used in real life. How does this relate to
logic-speak? Students might enjoy inventing logic-speak sentences
such as:
'I really like eating ice cream XOR chicken curry' (meaning I
like ice cream and curry, but not at the same time)
'I like tea XNOR milk' (meaning I only like tea with
milk)
Key questions
- Describe what you see.
- What are we supposed to change? What are we supposed to leave
fixed?
- How might we record our findings?
- What happens if the switches in the two pairs of circuits are
set to the same values?
Once students feel that they have described the gates clearly
using English, usethis follow up
- How could you represent the behaviour of the gate
symbolically?
Possible extension
Once the concept of the gate is understood there are several
follow up questions, such as
Simple
Counting Machine .
Possible support
You might suggest focussing on the AND, OR and NOT gates to begin
with