What happens when current flow exceeds the rating of a fuse in a circuit?

What happens when current flow exceeds the rating of a fuse in a circuit?

• A. The fuse melts and opens the circuit.
• B. The circuit breaker trips.
• C. The wire overheats but current continues.
• D. The fuse strengthens and keeps conducting.

Answer: (A)

When current exceeds the fuse rating, the metal link inside the fuse heats up from I^2R losses and eventually melts, opening the circuit. This interruption stops the flow of current to protect wiring and connected devices from overheating or fire. The rating is set so that at that current level, the fuse will blow within a specified time to prevent damage. If the overload is only brief, some fuses may not blow immediately, depending on the fuse type (fast-acting versus slow-blow). The other ideas aren’t what a fuse does: a circuit breaker trips as a separate device, the wire overheating with current continuing would defeat protection, and a fuse doesn’t strengthen or continue conducting.

When current exceeds the fuse rating, the metal link inside the fuse heats up from I^2R losses and eventually melts, opening the circuit. This interruption stops the flow of current to protect wiring and connected devices from overheating or fire. The rating is set so that at that current level, the fuse will blow within a specified time to prevent damage. If the overload is only brief, some fuses may not blow immediately, depending on the fuse type (fast-acting versus slow-blow). The other ideas aren’t what a fuse does: a circuit breaker trips as a separate device, the wire overheating with current continuing would defeat protection, and a fuse doesn’t strengthen or continue conducting.