Power in an electrical system is measured with which instrument?

Power in an electrical system is measured with which instrument?

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

Answer: (B)

Measuring power requires an instrument that directly reads real power, which is the rate at which energy is actually transferred. A wattmeter is designed to do this by combining voltage and current in a way that accounts for their phase relationship in AC circuits, so it shows power in watts. In other meters, a voltmeter only reads voltage, an ammeter only reads current, and an ohmmeter measures resistance; none of these directly give real power. In DC, power is simply P = V × I, but a wattmeter still provides the direct reading of that product, making it the appropriate tool for measuring power.

Measuring power requires an instrument that directly reads real power, which is the rate at which energy is actually transferred. A wattmeter is designed to do this by combining voltage and current in a way that accounts for their phase relationship in AC circuits, so it shows power in watts. In other meters, a voltmeter only reads voltage, an ammeter only reads current, and an ohmmeter measures resistance; none of these directly give real power. In DC, power is simply P = V × I, but a wattmeter still provides the direct reading of that product, making it the appropriate tool for measuring power.