In a circuit with resistors R1 through R5, which resistor, when disconnected, leaves the ohmmeter reading the same as when all resistors are connected?

• A. R1
• B. R5
• C. R2
• D. R3

Answer: (B)

When an ohmmeter measures resistance, it looks at the equivalent resistance between its two terminals. If a direct conductor (a short) exists across those terminals, the total resistance becomes essentially the short’s low value, and any resistor that is connected in parallel with that short doesn’t affect the reading.

R5 is arranged in the network such that it is effectively bypassed by a short path across the measurement terminals. Because the current prefers the short path, R5 doesn’t contribute to the total resistance, so whether it is connected or disconnected leaves the ohmmeter reading unchanged.

The other resistors aren’t bypassed in that way, so disconnecting them would change the total resistance seen by the ohmmeter.