Many schools have home-made versions containing a small bicycle dynamo, mounted on a board with a handle. When the handle turns, electricity is made which lights a small lamp. Dynamos are easy to come by from cycle shops and the wiring is simple- connect it in the place of a battery in a simple lamp circuit.
If you prefer to buy a ready-made kit, lab suppliers have several different varieties to choose from. They vary in both complexity and price. Some contain integral lamps, others may be connected to external lamps or a voltmeter.
A dynamo is basically an electric motor that works in reverse, small motors can actually be used to generate electricity – by fixing a small propeller (available from science or technology suppliers) to the motor shaft and connecting to a sensitive voltmeter a current will flow when the propeller turns. A model wind turbine can be made in this way.
A dynamo uses the principle of electromagnetic induction when in operation- essentially a magnet rotates within a coil of wire to produce a current.
As examples of dynamos in action, dynamo powered torches and radios are now available in highstreet stores as well as through lab suppliers.
Dynamos are often referred to as turbines when describing the types that create high voltages, such as the turbines in hydroelectric plants.