AC Coil Example

120 volts at 60 Hz is applied to the coil. Since it has an iron core, a large alternating magnetic field is produced.

The magnetic field alternates 60 times per second, being produced by an AC, iron core coil. The changing magnetic field induces a voltage in the coil which is sufficient to light the bulb if it is close enough.

When you bring the bulb close enough for it to produce light, you are demonstrating the action of a transformer, which uses the changing magnetic field produced by the current in one coil to induce a voltage into a second coil. This is an example of Faraday's law.