alleryStart learning →What do fuses and circuit breakers do in a circuit?
AClose the circuit when voltage drops low
BOpen the circuit when current exceeds a limit
CReduce the voltage supplied to an appliance
DStore charge until the current settles down
Answer & Solution
Correct answer: B. Open the circuit when current exceeds a limit
1. Overheating of supply wires is driven by the current they carry, through P = I squared R_w.
2. Limiting the current therefore limits the heating.
3. Both fuses and breakers open the circuit automatically once a sustained current passes a safe limit.
4. A fuse does it by melting a metal strip and must be replaced, while a breaker uses a bimetallic strip and can be reset.
5. Neither device reduces the supply voltage, so option three describes a transformer instead.
_Source: OpenStax College Physics (CC BY 4.0), Ch 20 "Electric Current, Resistance, and Ohm's Law", section Thermal Hazards_
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