To measure DC voltage with proper polarity, how should the voltmeter be connected?

• A. Positive to negative and negative to positive
• B. Polarity does not matter
• C. Both leads to the same node
• D. Negative to negative and positive to positive

Answer: (D)

Polarity matters when measuring DC voltage because a voltmeter reads the potential difference between its two leads, and the sign of that reading depends on which lead is connected to the higher-potential point in the circuit. To measure DC voltage with proper polarity, connect the voltmeter’s positive input to the circuit’s positive side and the voltmeter’s negative input to the circuit’s negative side. In practical terms, use the red lead on the higher-potential node and the black lead on the lower-potential node. This alignment gives a positive reading that reflects the actual source voltage; reversing the leads would yield a negative reading, and placing both leads on the same node would read zero since there’s no potential difference.