Strip the insulation off the end of a long piece of copper wire and wrap it 40 times around a cylinder of soft iron, to make a solenoid[?]. [If you can use a U-shaped piece of soft iron then so much the better]. Connect the ends of the wire into the power supply using crocodile clips or other suitable connectors. This is called a primary coil[?]. Connect a 6V bulb in parallel[?] with the solenoid.
Now take another long piece of wire. Strip the ends, and either: wrap it around the same soft iron core 60 times or [even better] if you have U-shaped soft iron cores; use a separate core to put the 30 turns on. This is called the secondary coil[?]
You should now have two pieces of bare ends from the second piece of wire. Connect them to a 6V bulb so that you have a loop that is independent of the power supply.
Turn on the power supply and [if applicable] join the two u-shaped soft iron cores together. Be careful, the primary coil will now be a powerful electromagnet.
Compare the brightness of the two bulbs.
Repeat with 20 turns on the secondary coil.
This is a quick and dirty demo. Suitable to teach the basics of transformers. Other experiments using professionally wound coils and oscilloscopes are more suitable for more advanced or older students.
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