Meter reading shows ground circuit within specification vs part of circuit with switch open?

• A. The meter reading guarantees the ground circuit is within specification.
• B. The meter reading shows there can be voltage in at least part of the circuit with the switch open.
• C. The meter reading confirms there is voltage in the entire circuit.
• D. The meter reading shows no voltage anywhere.

Answer: (B)

The key idea is what a meter reading means when a circuit is not complete. A ground path being within specification tells you about the return path’s quality, not about voltage presence once a switch is opened. When a switch is open, part of the circuit is electrically isolated from the source, so there is no current flowing, but the source can still establish a potential on the isolated side. A voltmeter, especially with high input impedance, can detect this potential even though the circuit isn’t energized in the sense of delivering current. That’s why you can have voltage present in at least part of the circuit with the switch open, even though the ground path itself tests as acceptable.

So the reading indicates that voltage may exist on the open side of the circuit, not that the entire circuit is energized or that the ground path is guaranteed good everywhere, nor that there is no voltage anywhere.