Take apart and reassemble a scalextric car and controller to show how it works
Scalextric Car, Wires, 9V battery. Also useful to have an electronics kit to show how a lightbulb dims when the current runs through a variable resistor
1) Take off the top shell to show the motor and wires
2) connect the battery to the contacts to make the motor run and wheels turn
3) show how the contacts carry the current to the motor
4) Take a controller apart to show how it varies the resistance.
5) Use an electronics lab kit to show what increasing the resistance does to a light bulb
6) explain that the greater the current the brighter the light bulb and the greater the current to the car the faster the motor turns the wheels to make the car go faster