To ensure a fuse protects the circuit conductors and components, it must be wired in series with the circuit.

• A. Across the supply
• B. In a separate branch
• C. In series with the circuit
• D. In parallel with the circuit

Answer: (C)

Fuses protect by interrupting current when they overheat from excessive current, so they must be placed in the path that carries the circuit current. When wired in series with the circuit, the same current that feeds the load also flows through the fuse; if an overcurrent occurs, the fuse melts and opens the circuit, stopping current to all components downstream and safeguarding conductors from overheating. If the fuse were placed across the supply or in parallel with the circuit, it would not interrupt the main current path to the load—either creating a direct short across the source or allowing current to bypass the protected path—so protection wouldn’t work as intended. Placing it in a separate branch would similarly shield only that branch and leave the rest of the circuit unprotected. Therefore, the fuse must be in series with the circuit to provide effective protection.