What device is used to measure large values of alternating current?

• A. Voltmeter
• B. Wattmeter
• C. Current transformer
• D. Amperemeter

Answer: (C)

A current transformer is specifically designed to measure large values of alternating current (AC) by converting the high current into a much lower, manageable current that can be accurately measured using standard instruments. The operation of a current transformer involves winding a primary coil around which the current flows, and a secondary coil that induces a smaller current proportional to the primary current. This allows for large currents to be monitored safely and effectively without direct contact with the high-voltage line, making it an essential tool in power generation and distribution systems.

While an amperemeter, or ammeter, can measure current, it is typically suited for lower currents rather than larger values, especially in high-voltage applications. A voltmeter is primarily used to measure voltage, and a wattmeter measures electrical power by combining voltage and current measurements. Therefore, the current transformer is the appropriate and specialized device for measuring large alternating currents safely and accurately.