During troubleshooting of an open circuit with a voltmeter connected across the circuit, which observation is expected?

• A. Create a low resistance path and the current flow will be greater than normal.
• B. Current flows and the lamp lights.
• C. Nothing appears on the voltmeter.
• D. Battery voltage appears on the voltmeter.

Answer: (D)

When you measure across an open circuit, the voltmeter should read the source voltage. The voltmeter has a very high input resistance, so it draws only a tiny, almost negligible current and doesn’t disturb the circuit. Since the circuit is open, no current flows through any load (like a lamp), so nothing changes in the circuit, and the meter simply shows the full potential difference provided by the battery. That’s why the reading is battery voltage on the voltmeter. If there were a short or a path for current, you’d see different behavior, and if there were no voltage present, the meter would read zero, which isn’t the case here.