Students build a motor into a simple electric circuit: a battery and motor, connected into a loop with wires, using masking tape to attach the wires to each component. When the loop of the circuit is closed, the shaft on the motor will turn, but often so fast that it might be hard to see - put your finger on it to feel it turn.
Once students have their motor working, show them the card stock and other materials, which they can tape to the shaft of the motor.
Fan - a small circle of card with angled blades blows air.
Saw - a small circle of card with a serrated edge can cut through a piece of tin foil or thin paper.
Colour wheel - add colours to a circle of card. When it spins the colours blur together.
Students can also add holiday lights into the circuit - see the helicopter in the last photo.