Making a transformer

A transformer is a device that converts one AC voltage to another. A detailed description of how they work is given elsewhere in wikipedia under transformer. The purpose of this page is to give details of how a transformer can be made very simply at home or in a classroom in order to teach the basic principles.

You will Need

• Some pieces of soft iron[?] preferable in a U shape but a cylinder will do.
• Plastic coated wire
• Some 6V mes bulbs[?] [torch bulbs] in a suitable bulb holder
• Connecting wire with 4mm plugs
• Crocodile clips[?]
• A 4V AC Power supply that is fitted with a 5A trip switch

Method

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.