A safety device that blows (melts) if the current exceeds a specified value.

A safety device that blows (melts) if the current exceeds a specified value.

• A. Fuse
• B. Ground
• C. Breaker
• D. Transformer

Answer: (A)

The device is a fuse. It works as a one-time overcurrent protector by carrying the normal current, but when the current exceeds its rating, the metal link inside heats up (I^2R heating) and melts, opening the circuit and stopping the current to prevent damage. Because it sacrifices itself, it must be replaced after it blows. In contrast, a ground is just a path to earth for fault currents, not a melting protection device; a breaker trips to interrupt current (and can be reset), not by melting; a transformer changes voltage, not provide overcurrent protection.

The device is a fuse. It works as a one-time overcurrent protector by carrying the normal current, but when the current exceeds its rating, the metal link inside heats up (I^2R heating) and melts, opening the circuit and stopping the current to prevent damage. Because it sacrifices itself, it must be replaced after it blows. In contrast, a ground is just a path to earth for fault currents, not a melting protection device; a breaker trips to interrupt current (and can be reset), not by melting; a transformer changes voltage, not provide overcurrent protection.