---
title: "Fuse vs MCB differences"
subject: "Basic Electrical and Electronics Engineering"
chapter: 4
key: "semester_1/basic_electrical_and_electronics_engineering:fuse-vs-mcb"
source: https://www.bctengineer.com/q/semester_1/basic_electrical_and_electronics_engineering/fuse-vs-mcb
site: BCT Engineering
---

# Fuse vs MCB differences

Basic Electrical and Electronics Engineering · Chapter 4: Electrical Installations

- Asked in: 2081 Baishakh (new course), 3 marks
- Video: [Circuit Breaker Vs Fuse | Key Differences | Working Principal Explained](https://www.youtube.com/watch?v=HjjIkNkJ2Dc) — Electrical lectures
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_1/basic_electrical_and_electronics_engineering/fuse-vs-mcb
- Whole chapter: https://www.bctengineer.com/md/semester_1/basic_electrical_and_electronics_engineering/chapter-4

## Question

What are the differences between fuse and MCB?

## 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.

## Answer

| 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.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. How does an MCB open the circuit compared with a fuse?
   A. MCB melts a wire; fuse uses a bimetal strip
   B. Both operate only by melting a wire
   C. MCB uses thermal and electromagnetic trip; fuse wire melts
   D. MCB uses a battery; fuse uses a magnet
   Answer: C. A fuse protects by its wire melting, while an MCB uses a bimetal (overload) and solenoid (short circuit) trip. (Key point: Operating mechanism)

2. What happens after a fault is cleared in each device?
   A. Fuse is reset by lever; MCB must be replaced
   B. Both must be replaced
   C. Both are reset by lever
   D. Fuse must be replaced or rewired; MCB is reset by switching the lever ON
   Answer: D. A blown fuse is single use, whereas an MCB can be reset by hand. (Key point: Reusability)

3. Which statement about cost and safety is correct?
   A. MCB has higher first cost but no replacement cost and is calibrated and safer
   B. Fuse has higher first cost and no replacement cost
   C. MCB is cheaper to buy and must be replaced after each trip
   D. Fuse is calibrated and tamper-proof, MCB is not
   Answer: A. MCBs cost more initially but avoid recurring replacement and are calibrated, tamper-proof and safer. (Key point: Cost and safety)

## Related in other subjects

- [Fuse vs MCB and HRC rupturing capacity](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Afuse-mcb-hrc-rupturing) — Industrial Power Distribution and Illumination, chapter 3, asked 3×
- [Fuse vs MCB; HRC fuse time terms](https://www.bctengineer.com/question.md?key=semester_6%2Fswitchgear_and_protection%3Afuse-vs-mcb-hrc-terms) — Switchgear and Protection, chapter 3
- [HRC fuse construction; fuse vs MCB](https://www.bctengineer.com/question.md?key=semester_6%2Fswitchgear_and_protection%3Ahrc-fuse-construction-vs-mcb) — Switchgear and Protection, chapter 3
- [MCB, MCCB and HRC fuse comparison](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Amcb-mccb-hrc-comparison) — Industrial Power Distribution and Illumination, chapter 3, asked 3×