Generally an alloy of lead and tin is used as a material of the fuse wire.

Question

Given below are two statements, one is labelled as Assertion (A) and the other as Reason (R).

Assertion (A): Generally an alloy of lead and tin is used as a material of the fuse wire.

Reason (R): Alloy of lead and tin has a higher melting point than copper and aluminium.

Select the correct answer from the code given below:

1. A. Both (A) and (R) are true, but (R) is not the correct explanation of (A)
2. B. (A) is false, but (R) is true
3. C. (A) is true, but (R) is false (Correct answer)
4. D. Both (A) and (R) are true and (R) is the correct explanation of (A)

Correct Answer

Option C — (A) is true, but (R) is false

Detailed Solution & Explanation

The correct answer is (A) is true, but (R) is false.

Key Points

• Assertion is true. A fuse wire is normally made of an alloy of lead and tin, chosen precisely because it melts easily.
• Reason is false. The lead-tin alloy has a LOW melting point, much *lower* than copper or aluminium — not higher. A fuse must melt before the circuit wiring does; a high melting point would defeat its whole purpose.
• (A) true and (R) false gives option (c).

Additional Information

• A fuse works on the heating effect of electric current (Joule's law, H = I²Rt). Excess current heats the thin fuse wire until it melts and breaks the circuit.
• A fuse wire must have high resistivity and a low melting point, and is always connected in series with the live wire.
• Domestic circuits are wired in parallel so appliances operate independently and each gets full voltage.
• The modern equivalent is the MCB (Miniature Circuit Breaker), which trips electromagnetically and can be reset instead of replaced.