How does a quiz-show buzzer know when to sound? What must happen in the wires for it to ring only at the right moment?
Hands up: what job do you think a switch does in a circuit?
How could two pieces of foil act as a switch for a quiz buzzer?
A switch opens or closes a gap so electricity can flow or stop. Without a complete path, nothing works.
A closed loop is a full path from one side of the battery, through the parts, and back again with no gaps.
Two pieces of foil can be contact points: metal surfaces that touch only when you want the circuit on, and that touch is the switch. Later you will use foil like that in your own circuit.
On the board is a circuit that is already complete: battery, buzzer, wires, no gaps. Watch what it does.
It buzzes, and it never stops.
A quiz buzzer only sounds when someone presses it. So what has to change? Where would you put the change, and what could sit in that space so the sound can be turned on and off?
Plan a switch-and-buzzer loop
Two things before the kit comes out, and they are the two that are hard to find by trial and error.
One: nothing happens at all unless the loop is complete, the whole way round, back to the battery.
Two: the gap needs two pieces of metal that can touch each other. Metal lets electricity through. Card, tape and plastic do not.
How you put yours together is your group's to work out.
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