This is a wonderful way to feel the conservation of energy. Turn the handle and switch on lights, and as you use more energy, turning the handle gets harder.

It is one of the most effective exhibits we have ever built, and even if you know what is going to happen it is somehow still surprising whether you are a 2 year old, or a physics grad.

Our generators are unusual because they use no gearing and no iron in the mechanism, so which means that with no electrical loads switched on it will keep spinning for tens of seconds, but a fully grown adult will struggle to turn the handle to light 100W of a heater, the increase in force when you switch on a load is extremely striking, and makes you think a little more when you turn on a light at home.

Also the internals of the generator is exposed. This allows you to see what is going on inside, and connect the mechanism to moving a magnet near a coil.

The generator could simply be connected to voltage, current and power meters to make the mathematical part of energy and power more approachable.

It can be made to look like it is attached to a source of energy on the back as we did with a water turbine in Lanark.

It can also be built into a version without the built in lights for doing demo lectures, or to mount them somewhere else.