Ham Radio General Class Practice Test

What causes a voltage to appear across the secondary winding of a transformer when an AC voltage source is connected across its primary winding?

1. Capacitive coupling

2. Displacement current coupling

3. Mutual inductance

4. Mutual capacitance

The correct answer is: Mutual inductance

The appearance of voltage across the secondary winding of a transformer connected to an AC voltage source on its primary winding is a result of mutual inductance. In a transformer, the primary winding creates a magnetic field when an AC current flows through it. This fluctuating magnetic field induces a voltage in the secondary winding through the principle of electromagnetic induction. The effectiveness of this process is dependent on the mutual inductance between the two windings, which refers to the ability of one coil to induce a voltage in another coil due to the shared magnetic field. This principle is fundamental to the operation of transformers and defines how energy can be transferred from one winding to another without the two electrical circuits being directly connected. The winding configurations and the core material used in the transformer enhance this mutual inductance, allowing for efficient voltage transformation from the primary to the secondary side. Understanding mutual inductance is crucial for comprehending how transformers function in a wide range of applications, from power distribution to signal processing in communications.