What is the maximum voltage a shunt resistor can be used with?

• A. Up to 120 Volts
• B. Up to 140 Volts
• C. Up to 240 Volts
• D. Up to 300 Volts

Answer: (B)

When a shunt resistor is used to measure current, the important limit is the voltage that can appear across the shunt without breaking down its insulation or compromising safety. The shunt has a rated maximum voltage between its terminals, and the measurement system (including any protection and isolation) must stay within that limit. In typical Con Edison basic practice equipment, that rating is about 140 volts. So the safe, practical maximum across the shunt is up to 140 volts.

Choosing a higher-voltage environment, like 240 or 300 volts, would require a shunt with a higher insulation rating or additional isolation in the measurement setup, which goes beyond the standard equipment used in basic practice. The value of 120 volts is safely within the limit, but it isn’t the maximum—140 volts is the upper bound for the common shunt configurations in this context.