Four Parts, Four Questions
- SOURCE: what keeps the electrons moving? A cell, a generator
- WIRE: which road do they travel along? Copper, usually covered
- SWITCH: how do we open and close that road?
- LOAD: what does the useful work? A bulb, a fan, a heater
Presenter notes: Hold up a cell, a bulb and one piece of wire, and ask the class to tell you how to light the bulb. Somebody will say join the wire from the cell to the bulb, so do exactly that, and nothing happens. Ask again. Eventually somebody says you need another wire, and now ask the question that runs the whole period: why two? Why does electricity need a return road, when water poured into a glass does not come back? Tell them that answering that properly explains why every appliance in their house has two wires, why one loose connection anywhere kills a whole circuit, and what a switch is really doing when it is off.