- 2081 Baishakh (new course) · 3 marks
Fuse vs MCB differences
Short answer
A fuse melts when overcurrent, needing replacement; an MCB trips via thermal (overload) and magnetic (short-circuit) mechanisms and can be reset. MCBs provide more precise, tamper-proof protection with visible trip indication, though costlier initially.
What are the differences between fuse and MCB?
| Point | Fuse | MCB (Miniature Circuit Breaker) |
|---|---|---|
| Operation | Fuse wire melts when the current exceeds its rating | An electromagnetic and thermal (bimetal) trip mechanism opens the contacts |
| Reuse | Single use; must be replaced or rewired after blowing | Can be reset by switching the lever ON after the fault is cleared |
| Speed | Operating time is less precise and varies with the fuse wire (especially rewirable fuses) | Trips with defined, repeatable time-current characteristics (B, C, D curves) |
| Protection | Overload and short circuit (by melting) | Overload (thermal) and short circuit (magnetic) |
| Indication | Fault location not obvious; the blown wire must be inspected | Lever position clearly shows the tripped state |
| Cost | Cheap initially, but replacement cost recurs | Higher first cost, but no replacement cost |
| Safety | A wrong rating or wire may be fitted by the user | Calibrated and tamper-proof, so safer |
| Use | Old wiring, small appliances | Modern consumer units, houses and offices |
An MCB can also be used as an ON/OFF switch, and it can be reset without opening the board.
✓ Answer checked by Claude Opus 5.5 (high effort)
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