To measure voltage with a multimeter, how should you connect the meter in the circuit?

• A. In parallel with the component
• B. In series with the component
• C. Across the power supply only
• D. Across ground only

Answer: (A)

Voltage is the difference in electric potential between two points, so to read it you need the meter placed across those two points. A multimeter is designed with very high input impedance, which means it draws almost no current when connected. Placing the meter in parallel with the component allows you to measure the exact voltage across that component without disturbing the circuit. If you put the meter in series, you’d insert it into the current path, alter the current flow, and effectively measure current rather than voltage. When you connect the probes, put the red lead on the higher-potential point and the black lead on the lower-potential (often ground). Measuring the supply voltage is simply a special case of this same parallel connection across the power terminals.