A transformer is a device that changes or transforms an alternating voltage to any desired value.

A transformer is a device that changes or transforms an alternating voltage to any desired value.

• A. Alternating Current
• B. Alternating Voltage
• C. Direct Current
• D. Current

Answer: (B)

The key idea is that a transformer changes the voltage of a signal, and it does so using the changing magnetic flux produced by an alternating input. Because the flux must continuously rise and fall to induce voltages in the secondary winding, the input must be alternating. So the thing being transformed is the voltage, not the current or the type of current. Direct current would quickly produce a steady magnetic field and only a brief transient on the secondary, so a controlled voltage change isn’t possible. While current can vary with the load, the transformer’s purpose is to alter the voltage level, making alternating voltage the best fit.

The key idea is that a transformer changes the voltage of a signal, and it does so using the changing magnetic flux produced by an alternating input. Because the flux must continuously rise and fall to induce voltages in the secondary winding, the input must be alternating. So the thing being transformed is the voltage, not the current or the type of current. Direct current would quickly produce a steady magnetic field and only a brief transient on the secondary, so a controlled voltage change isn’t possible. While current can vary with the load, the transformer’s purpose is to alter the voltage level, making alternating voltage the best fit.