Where should a voltmeter be connected to measure voltage in a circuit?

• A. In series with the load to be measured.
• B. Across the source.
• C. In parallel with the load to be measured.
• D. Across the ammeter.

Answer: (C)

Voltmeter measures the potential difference, so it must be connected in parallel with the component whose voltage you want to know. Placing it in parallel lets the meter read the same voltage drop as across that element while drawing very little current because a voltmeter has high internal resistance. If you put it in series, it would become part of the circuit and disturb the current, giving an incorrect reading. Therefore, to measure the voltage across a load, connect the voltmeter across that load—in parallel with it. Connecting across the source would show the supply voltage, which isn’t the same as the load’s voltage if other elements are involved, and across an ammeter isn’t the standard way to measure a load’s voltage.