How to Build a Simple Transformer Coil

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A transformer, a device in which a magnetic field couples two circuits while linked to each, converts one AC voltage to another. A transformer typically converts between high and low voltages. A step-up transformer raises voltage while a step-down transformer lowers voltage. The ideal transformer has a perfect magnetic coupling and all the power fed into the transformer is available at the output, but in reality there are losses. A demonstration transformer, made very easily, teaches the basic principles of a transformer.

    Use the wire stripper to strip the insulation off the end of a long piece of copper wire. Wrap it 30 times around a cylinder of soft iron to make the solenoid. Use the alligator clips to connect the two ends of the wire into a power supply. Connect a 6-volt bulb parallel with the solenoid to make a primary coil.

    Strip the ends off another long piece of wire. Wrap the wire 60 times around the same soft iron core to make the secondary coil.

    Connect the two bare ends from the second piece of wire to a 6-volt bulb.

    Turn on the power and join together the two soft iron cores to make the primary coil a powerful electromagnetic.

    Compare the brightness of the bulbs to see that the secondary is much brighter. Repeat with 15 turns on the secondary coil and everything is much dimmer.

    Things You'll Need

    • Wire stripper
    • U shape or cylinder shape soft iron pieces
    • Plastic-coated wire
    • 6-volt mes bulbs
    • Suitable bulb holder
    • 4-mm plugs
    • Connecting wire
    • Alligator clips
    • 4-volt AC power supply fitter with a 5-amp trip switch


    • Never plug this homemade transformer into a home electrical outlet.

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