A transformer is a device that does what to the voltage of alternating current?

• A. Increases or decreases the voltage of alternating current
• B. Stores energy in a magnetic field
• C. Rectifies AC to DC
• D. Provides isolation between circuits

Answer: (A)

The main idea is that a transformer changes the voltage level of alternating current using mutual induction between its primary and secondary windings. The secondary voltage is determined by the turns ratio: more turns on the secondary give a higher voltage (step up), fewer turns give a lower voltage (step down). In an ideal transformer, power stays the same, so the current moves inversely with voltage. This is why transformers are used to move voltage up for transmission and down for consumer use. The transformer itself doesn’t store energy for later use (that role belongs to energy storage components like inductors or capacitors) and it doesn’t convert AC to DC (that’s done by rectifiers). Some transformers do provide isolation between circuits, but that’s not the primary purpose; the essential function is altering voltage.