The ball run consists of a steel sheet, that you can use magnets to attach various tubes gullies and other devices for the ball to run down
To get the ball back up to the top there are a series of blowers set back into the wall (so you can bridge over them with the tubes and build even more complex ball runs).
This is probably the simplest generator that can produce a noticible amount of power, and is used in the torches you shake to power them.
There are two LEDs on each coil, one will light if the induced current is clockwise and the other if it is anti-clockwise. One will flash as the north pole move into the coil and one as the south pole does.
Though it is a classic, it has got a lot more effective with the introduction of rare earth magnets. You can investigate how the voltage produces is affected by where the magnet is moved, how fast it is moved, how strong the magnet is and how many turns the coil has.
To make the experience more intuitive this version visualises the flow of electricity with a flow of led lights.
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.
Dry ice based cloud chambers are quite common, you cool a plate at the bottom and create a chamber full of alcohol vapour. The vapour cools as it falls and eventually becomes supersaturated, and any ionising radiation creates tracks of cloud. They are great, but dry ice is a pain to get hold of.
Something which emits a particular colour of light will also absorb it, so the edge of a sodium 'flame test' will look dark when illuminated by a sodium light producing a strange dark flame.