When teaching series circuits to my GCSE students, I use a striped rope to demonstrate how the circuit works. The students form a circle loosely holding the large ring of rope with both hands.
- I designate one student to be the cell, and they feed the rope between their hands driving it to move around the circle. The stripes on the rope represent the charge flowing around the circuit. We notice that the charge starts to move everywhere in the circuit at exactly the same time.
- I designate several other students to be ammeters; they count the stripes on the rope as it passes through their hands. This represents measuring the current (the amount of charge that passes per second) and they count the same number of stripes as each other because the current is the same everywhere in the circuit.
- I designate another student to be a bulb. They now close their hands a little tighter around the moving rope and they begin to feel their hands warming up from the friction. This represents the resistance in the bulb. The heating caused by the resistance of the current in the thin filament wire is what causes the bulb to heat up.
Modelling the circuit in this way really helps students to understand current, potential difference and resistance in a circuit.