A reading of 0 V in a circuit may mean that the switch is closed.

A reading of 0 V in a circuit may mean that the switch is closed.

• A. The circuit is energized.
• B. The switch is closed.
• C. There is no current flow.
• D. The voltage source is disconnected.

Answer: (B)

When you measure 0 V across a switch, it’s because a closed switch acts like a conductor with negligible resistance, so the two points it connects are at the same electrical potential and there’s essentially no voltage drop across it. In other words, the meter sees no difference when the switch is conducting. If the switch were open, you’d typically see the source voltage appear across the switch (or the circuit would be open and no current would flow through that path), depending on exactly where you place the meter. So a 0 V reading here doesn’t mean the whole circuit is energized, nor does it guarantee the source is disconnected; it mainly indicates the switch is closed and there’s no voltage drop across it.

When you measure 0 V across a switch, it’s because a closed switch acts like a conductor with negligible resistance, so the two points it connects are at the same electrical potential and there’s essentially no voltage drop across it. In other words, the meter sees no difference when the switch is conducting. If the switch were open, you’d typically see the source voltage appear across the switch (or the circuit would be open and no current would flow through that path), depending on exactly where you place the meter. So a 0 V reading here doesn’t mean the whole circuit is energized, nor does it guarantee the source is disconnected; it mainly indicates the switch is closed and there’s no voltage drop across it.