The wattmeter measures true power in a circuit; two basic types are dynamic and electronic.

The wattmeter measures true power in a circuit; two basic types are dynamic and electronic.

• A. Oscilloscope
• B. Voltmeter
• C. Wattmeter
• D. Ammeter

Answer: (C)

Real power in an AC circuit is the actual energy transfer rate, and a wattmeter is designed to read that quantity directly by taking into account both voltage and current and their phase relationship. It measures P = VI cosφ, so it reflects true power rather than just voltage or current separately. The two common implementations—dynamic (electrodynamometer-based) and electronic—provide different ways to sense that product while accounting for the phase angle. An oscilloscope shows waveforms and can be used to analyze power with extra steps, but it isn’t a dedicated true power meter. A voltmeter only measures voltage, and an ammeter only measures current, so neither alone captures real power.

Real power in an AC circuit is the actual energy transfer rate, and a wattmeter is designed to read that quantity directly by taking into account both voltage and current and their phase relationship. It measures P = VI cosφ, so it reflects true power rather than just voltage or current separately. The two common implementations—dynamic (electrodynamometer-based) and electronic—provide different ways to sense that product while accounting for the phase angle.

An oscilloscope shows waveforms and can be used to analyze power with extra steps, but it isn’t a dedicated true power meter. A voltmeter only measures voltage, and an ammeter only measures current, so neither alone captures real power.