Where would the voltmeter read 0 volts in a single-load circuit?

• A. After the load
• B. Before the load
• C. Across the load
• D. Across the source

Answer: (B)

A voltmeter measures the potential difference between two points. In a simple circuit with ideal wiring, the conductors have negligible resistance, so there’s essentially no voltage drop along the wires. All the supply voltage appears across the load.

So, connecting the voltmeter across a section of wire before the load puts both probes at the same potential, yielding about 0 volts. If you connected across the load, you’d read the full supply voltage, and across the source you’d read the source voltage. After the load would also read 0 volts for the same reason—the wire there has little to no resistance and no voltage drop.