Testing the coil.

With the coil made, and embedded in a block of balsa with a clear plastic cover, it was time for some junoir help :)

My 5 year old son and 7 year old daughter discovered how a battery and a coil can attract or throw magnets.

To make life easier for my children, I connected a Lego Technic battery box (9v, 6 x 1.5v AA batteries). The battery box has a 'forward' 'reverse' switch, ideal for quickly changing the voltage directing through the coil... and making magnets dance.
Note Using batteries directly connected to a coil like this is potentially hazardous, as the batteries are trying to deliver more amps than they can. A battery may overheat and explode!. If you let your children try this, supervise them!
Ideally you should have a resistor between the batteries and coil to limit the current of the circuit, protecting your batteries and yourself!

The image below shows a heavy duty, 18 ohm resistor in the circuit, limiting the current to 346 ma. Without the resistor, the current is around 8 amps and as the batteries can only deliver 750 ma, they would soon overheat leading to potential personal injury.
As it was, I left the switch on for about 4 minutes, the coil and batteries remained cool, the resistor got very hot!

In the image above, you can see the coil's magnetic field on some magnetic viewing film... compare the strength of the field to the image below, the circuit below did not have the resistor in place!

The coils I make using the winder, are going to be part of an alternator for a wind generator. I also have an idea for dancing Ferrofluid :)

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