What is the primary function of a transformer?

• A. To store electrical energy in magnetic fields
• B. To convert current from one potential difference to another
• C. To generate electricity from fuel
• D. To measure voltage

Answer: (B)

The essential idea is that a transformer changes voltage levels using electromagnetic induction. When alternating current flows in the primary, it creates a changing magnetic flux in the core that links to the secondary winding, inducing a voltage there. The secondary voltage depends on the turns ratio between windings, so the device can increase or decrease the voltage while roughly keeping the same power (minus losses). This is why its primary function is to convert the potential difference from one level to another, enabling stepping voltages up for transmission or down for distribution.

It’s not meant to store energy, generate electricity from fuel, or measure voltage. It relies on AC because a changing current is needed to produce the changing magnetic field; steady DC wouldn’t produce a continuous output.