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. 120伏特、60赫兹的电压加到线圈上。由于其有铁芯，会产生较大的交变磁场。

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. 磁场每秒交替60次，由一个交流电铁芯线圈产生。变化的磁场在线圈中感应出电压，如果灯泡足够接近，该电压足以点亮灯泡。

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.