The correct way to connect a test voltmeter in a circuit is

• A. Between the source voltage and the load.
• B. In series with a unit.
• C. In parallel with a unit.
• D. Across the load.

Answer: (C)

Voltage is the potential difference between two points, so a voltmeter must be connected across the two terminals of the element you want to measure. Connecting the meter in parallel with the load lets it sample the same two nodes and read the exact voltage across that load, without drawing significant current thanks to the meter’s high internal resistance. If the meter were placed in series with the circuit or with the load, it would become part of the current path and alter the current flow, giving a reading that doesn’t reflect the load’s actual voltage. So, the proper way is to connect the voltmeter across the load, i.e., in parallel with it.