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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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Main function of fuse is to
Protect the line
Open the circuit
Prevent excessive current
Protect appliance
Prevent excessive current
Quick Summary: The main function of a fuse is to prevent excessive current from flowing in an electrical circuit. By acting as a sacrificial protective device, it interrupts the circuit when the current exceeds a pre-determined rated limit.
The main function of a fuse is to prevent excessive current from flowing in an electrical circuit. By acting as a sacrificial protective device, it interrupts the circuit when the current exceeds a pre-determined rated limit.
H=I2Rt — Joule's Law of heating, where H is heat, I is current, R is resistance, and t is time.
Ifuse≈VP — Approximate rating calculation for a fuse based on power and voltage.
The fuse operates on the heating effect of electric current, defined by Joule's Law H=I2Rt. When current exceeds the rated value, the heat generated causes the thin metallic fuse element to melt. This breaks the physical connection, effectively creating an open circuit that stops the flow of current to the protected load.
Fuses are connected in series with the load to ensure all current passes through them.
The fuse element is typically made of materials with low melting points like lead, tin, or copper alloys.
Fuses provide protection against both short-circuits and overloads.
It is a non-renewable (or one-time use) protection device compared to a Circuit Breaker.
Simple construction and low cost.
Provides reliable, fast-acting protection for sensitive equipment.
No maintenance required during normal operation.
Must be replaced after each operation (one-time use).
Cannot be used for switching purposes.
Probability of fuse element deterioration over time.
Residential domestic wiring.
Automotive electrical systems.
Small electronic devices and appliances.
Industrial control circuits.
The 'Excessive Current' (Option C) is the primary cause that triggers the 'Open Circuit' (Option B). While Option B and D are outcomes, Option C describes the direct functional intent of the fuse.
A standard fuse must have a breaking capacity higher than the maximum potential fault current of the circuit.
C is correct — The fundamental purpose of a fuse is to limit the flow of current to a specified safe value, thereby preventing damage to circuits and appliances.
Always remember that fuses protect against over-current, whereas relays/breakers are used for control and resettable protection.