What is a transformer used for?

• A. To convert direct current to alternating current
• B. To change the voltage level of alternating current
• C. To increase the resistance in a circuit
• D. To measure electrical power

Answer: (B)

A transformer is specifically designed to change the voltage level of alternating current (AC). It operates on the principle of electromagnetic induction, using two coils of wire, known as the primary and secondary windings, which are magnetically coupled. When alternating current flows through the primary winding, it creates a changing magnetic field that induces a current in the secondary winding.

The ratio of turns between the primary and secondary coils determines whether the voltage is stepped up (increased) or stepped down (decreased). This is vital in power distribution systems, where high voltage levels are often used to minimize energy loss over long distances, and then transformed to lower voltages for safe use in homes and businesses.

Other options are not applicable because a transformer does not convert direct current to alternating current, increase resistance, or measure electrical power. Each of those functions involves different electrical components and principles not related to a transformer's operation.