The correct option is 1 and 2 only
Explanation
An electric fuse is a safety device used in household circuits to protect electrical appliances and wiring from damage caused by excessive current. It operates based on the heating effect of electric current (Joule’s Heating).
Statement-wise Analysis
- Statement 1 is Correct: The primary function of a fuse is to prevent damage to appliances and the circuit itself. It achieves this by interrupting the flow of current when it exceeds a specified safety limit.
- Statement 2 is Correct: The fuse wire is made of a material with a low melting point (usually an alloy of lead and tin). When current exceeds the rated value, the heat generated ($H = I^2Rt$) causes the wire to melt and break the circuit, thereby stopping the current flow.
- Statement 3 is Incorrect: An ideal fuse should have low resistance so that it does not cause a significant voltage drop or power loss under normal load conditions. While the specific resistivity of the fuse material is higher than that of copper connecting wires, the overall resistance of the fuse element is kept low to ensure normal circuit operation. It is not intended to increase circuit resistance.
- Statement 4 is Incorrect: A fuse protects against both overloading and short-circuits.
- Overloading: Occurs when too many appliances draw current simultaneously, exceeding the circuit's capacity.
- Short-circuit: Occurs when the live and neutral wires come into direct contact, causing resistance to drop to near zero and current to spike dangerously high.
Key Takeaway: An electric fuse is a safety device with low resistance and a low melting point that protects circuits from both overloading and short-circuits by melting when current exceeds the rated limit.