Both analog and digital voltmeters measure __________.

• A. Potential difference
• B. Current
• C. Resistance
• D. Power

Answer: (A)

Voltmeters, whether analog or digital, measure the potential difference between two points in a circuit—the voltage. This tells you how much electrical energy per unit charge exists to move from one point to the other. To measure without disturbing the circuit, the voltmeter is connected in parallel with the component being measured and is designed with a very high internal resistance, so it draws only a tiny current. Analog voltmeters use a moving-coil mechanism to display a needle against a scale, while digital voltmeters show a numeric readout from an analog-to-digital converter. Current is measured by an ammeter, resistance by an ohmmeter, and power is usually determined from voltage and current (P = VI) rather than read directly from a voltmeter.