A device that increases or decreases the voltage of alternating current?

A device that increases or decreases the voltage of alternating current?

• A. Generator
• B. Solenoid
• C. Transformer
• D. Electric Motor

Answer: (C)

Transformers use electromagnetic induction to change the voltage of alternating current. Two coils wrapped around a magnetic core transfer the energy: when the current in the primary coil changes, it makes the magnetic flux in the core vary, which induces a voltage in the secondary coil. The size of the output voltage depends on the turns ratio between the coils: more turns on the secondary give a higher voltage (step-up), fewer turns give a lower voltage (step-down). In an ideal transformer, power is conserved, so the output power roughly equals the input power (VsIs ≈ VpIp), with current adjusting to keep the power balance. This only works with alternating current because a changing current is needed to produce a changing magnetic flux that induces the secondary voltage. A steady DC current would quickly produce a constant flux and then no further induction. The other devices don’t perform this voltage transformation: a generator creates electrical energy from mechanical energy, a solenoid is simply a coil that can act as an inductor or electromagnet, and an electric motor converts electrical energy into mechanical energy rather than transforming voltage levels.

Transformers use electromagnetic induction to change the voltage of alternating current. Two coils wrapped around a magnetic core transfer the energy: when the current in the primary coil changes, it makes the magnetic flux in the core vary, which induces a voltage in the secondary coil. The size of the output voltage depends on the turns ratio between the coils: more turns on the secondary give a higher voltage (step-up), fewer turns give a lower voltage (step-down). In an ideal transformer, power is conserved, so the output power roughly equals the input power (VsIs ≈ VpIp), with current adjusting to keep the power balance.

This only works with alternating current because a changing current is needed to produce a changing magnetic flux that induces the secondary voltage. A steady DC current would quickly produce a constant flux and then no further induction. The other devices don’t perform this voltage transformation: a generator creates electrical energy from mechanical energy, a solenoid is simply a coil that can act as an inductor or electromagnet, and an electric motor converts electrical energy into mechanical energy rather than transforming voltage levels.