Which device changes the amplitude of alternating current in power distribution?

Which device changes the amplitude of alternating current in power distribution?

• A. Inductor
• B. Transformer
• C. Diode
• D. Capacitor

Answer: (B)

The key idea is that changing the voltage (amplitude) of alternating current in power systems is done with a transformer, which uses mutual induction between two windings. When AC flows in the primary winding, it creates a changing magnetic flux in the core. That changing flux links to the secondary winding and induces a voltage there. The size of that induced voltage depends on the turns ratio between the windings. More turns on the secondary raise the voltage; fewer turns lower it. This lets us step up voltage for long-distance transmission and step it down for safe distribution to homes, all while keeping the frequency the same. Inductors mainly resist changes in current and are used for managing transient responses or filtering; they don’t reliably change the amplitude of a power line. Diodes convert AC to DC, not suitable for transforming AC amplitude. Capacitors store and release energy to smooth or filter voltage, but they don’t provide the controlled, proportional voltage transformation that a transformer does.

The key idea is that changing the voltage (amplitude) of alternating current in power systems is done with a transformer, which uses mutual induction between two windings. When AC flows in the primary winding, it creates a changing magnetic flux in the core. That changing flux links to the secondary winding and induces a voltage there. The size of that induced voltage depends on the turns ratio between the windings. More turns on the secondary raise the voltage; fewer turns lower it. This lets us step up voltage for long-distance transmission and step it down for safe distribution to homes, all while keeping the frequency the same.

Inductors mainly resist changes in current and are used for managing transient responses or filtering; they don’t reliably change the amplitude of a power line. Diodes convert AC to DC, not suitable for transforming AC amplitude. Capacitors store and release energy to smooth or filter voltage, but they don’t provide the controlled, proportional voltage transformation that a transformer does.