Lighting apparatus

When a magnetophile physics teacher creates new experiment stations, it might look something like this (see photo).

I developed this piece in 2005 for a science festival in Korea, and it garnered much admiration.

Below is the description, which is aimed at the experimenting visitors:

What to do?

1. Hold the transparent tube vertically in front of you so that you are looking at the small lamps inside.
2. Quickly turn the tube upside down by rotating it 180 degrees. This will cause two sphere magnets inside the tube to fall.

What to observe?

1. Observe the little lamps while the balls in the tube fall through the small coils of copper wire.
2. Repeat the process several times and make sure that the pair of balls can fall quickly.
3. Pay particular attention to the first and last little lamp.

This will help you understand:

A pair of 2 magnetic spheres falls inside the vertical tube. They have a magnetic field around them. The spheres fall through the inside of the copper wire coils. The small coils with 200 windings initially have no magnetic field inside them. But when the two spheres fall through the coil, they introduce their magnetic field into the coil: Suddenly there is a magnetic field in the coil too. Thus, the magnetic field in the coil changes from 'zero' to 'strong'.

When the magnetic field in a coil changes, an electrical voltage is induced (generated) in the coil. If the circuit of the coil windings is closed, an electric current flows.

A small lamp is soldered between the two wire ends of each coil. The coil is therefore closed via the small lamp. The electric current flows through the lamp and the lamp lights up.

When the spheres start at the top, they are not yet fast enough to generate a strong change in the magnetic field inside the coil. This is why the 1st little lamp usually does not light up.

But these are no ordinary little light bulbs. They are light-emitting diodes that need much less electrical energy to light up.