What is the electrical device that converts voltage from high to low or low to high?

• A. Transformer
• B. Inverter
• C. Regulator
• D. Rectifier

Answer: (A)

A transformer changes voltage levels of alternating current by using electromagnetic induction between two coils wrapped around a magnetic core. The input voltage applied to the primary induces a voltage in the secondary coil, and the ratio of turns between the two windings determines whether the output voltage is higher or lower. More turns on the secondary produce a higher voltage (step-up), fewer turns produce a lower voltage (step-down). Because it relies on a changing magnetic flux, a transformer only works with AC; applying DC initially may cause a momentary surge but then no energy is transferred. In an ideal case, power in roughly equals power out, so increasing voltage decreases current and vice versa. This is why transformers can either raise or lower voltage levels in power systems.

Inverter, regulator, and rectifier serve different roles: an inverter converts DC to AC, a regulator maintains a steady voltage, and a rectifier converts AC to DC. None of these are described by “converts voltage from high to low or low to high” for AC signals, which is the transformer’s job.