What is the principle of operation of a transformer?

• A. Electromagnetic induction
• B. Resistive heating
• C. Circuit resonance
• D. Capacitive coupling

Answer: (A)

The principle of operation of a transformer is based on electromagnetic induction. This fundamental concept involves the transfer of electrical energy between two or more circuits through the magnetic field produced by alternating current (AC).

In a transformer, when an AC voltage is applied to the primary winding, it creates an alternating magnetic field. This magnetic field magnetically couples to the secondary winding, inducing a voltage. The amount of voltage induced in the secondary winding depends on the turns ratio between the primary and secondary windings, which determines whether the transformer steps up or steps down the voltage.

Understanding electromagnetic induction is crucial since it is not just the mechanism behind the transformer's operation but also underlies various applications in electrical systems where voltage transformation is needed. Other concepts like resistive heating, circuit resonance, and capacitive coupling do not play a role in this process and are thus not applicable in describing how transformers function.