Which of the following describes the effect of overloading a fuse?

• A. The circuit breaker trips
• B. The circuit remains energized
• C. The heat melts the metal, opening the circuit
• D. The fuse glows but stays closed

Answer: (C)

When a fuse is overloaded, the current exceeds what the fuse is designed to carry. The fusible link inside is a thin piece of metal that heats up as current flows (power dissipated is I^2R). If the current is large enough, the heat raises the element to its melting point, causing it to melt and break the conductor. That interruption opens the circuit and stops the current flow, protecting the wiring and devices from damage. After blowing, the fuse can’t reset itself and must be replaced. The other statements describe outcomes of different protection mechanisms or situations that don’t match how a fuse operates (a circuit breaker trips, the circuit staying energized, or a fuse merely glowing and staying closed).