Build a working circuit, then break it on purpose
ObjectiveTo build a simple electric circuit, to show that it only works as a complete loop, and to find out what a switch actually does.
MaterialsOne dry cell of 1.5 volts, a small torch bulb with a holder, two or three pieces of connecting wire, tape, and two drawing pins pushed into a small piece of wood or card to make a home made switch. A paper clip laid across the two pins works as the switch itself.
MethodFirst, join a wire from one pole of the cell to one side of the bulb holder. Second, join a wire from the other side of the bulb holder to one pin of your switch. Third, join a wire from the other pin of the switch back to the other pole of the cell, so that the whole thing forms one closed loop. Fourth, lay the paper clip across both pins and watch the bulb. Fifth, lift the clip off one pin and watch it again. Sixth, put the clip back, and this time loosen one wire at the cell instead. Record what happens each time.
Discussion and conclusionDraw the circuit you made as a symbol diagram. Does it matter where in the loop you make the break? What does that tell you about how a switch works? And name the source, the wire, the switch and the load in your own circuit.