Where should a voltmeter be connected to measure the voltage across a component?

• A. In parallel with the component
• B. In series with the component
• C. Across the power supply
• D. Across the entire circuit

Answer: (A)

To measure the voltage across a component, you need the meter to read the potential difference between the two points at the component’s terminals. Connecting a voltmeter in parallel with the component does exactly that: it shares the same two nodes, so the meter’s reading equals the voltage across those terminals. The voltmeter is designed with relatively high internal resistance, so it draws very little current and doesn’t noticeably affect the circuit.

If the meter were placed in series, it would become part of the current path and alter the current flow, giving an incorrect reading for the component’s voltage. If you connect it across the power supply or across the entire circuit, you’d be reading the supply voltage or the total voltage drops, not the voltage across that particular component.