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a transformer can generate a magnetic field. which of the following choices correctly describes how a transformer is used to generate a magnetic field?

1. when the switch is open, current flows through the coil and induces a magnetic field.

2. when the switch is closed, current flows through the coil and induces a magnetic field.

3. when the switch is closed, a magnet is brought over to the coil to induce the magnetic field.

4. when the switch is open, a magnet is brought over to the coil to induce the magnetic field.

As a transformer generates ac current of different voltage when the switch is closed and the current flows in the primary coil which induces a magnetic field.

Option 2

Explanation:

A transformer is an electric device which can vary the potential differences or voltages of an alternating current. It's a simple device composed of an iron core, a primary and the secondary current conducting coil.

The primary coil is attached to the switch which provides ac current through potential difference. Now this current induces a magnetic field in the iron core. When the voltage of this ac current is varied, the magnetic field varies and starts inducing ac current of different voltage in the secondary coil.

Thus, an AC current of different voltage flows in the secondary coil that can be used in small electric devices. This is how a transformer works. There are two kinds of transformers- Step Up and Step Down. A step up transformer increases the potential difference whereas the step down does the opposite.