Q1. [1] § 11.7.1 Practical Applications of Heating Effect of Electric Current
Assertion (A) : Nichrome is an alloy which is commonly used in electrical heating devices such as electric irons, toasters, etc.
Reason (R) : The resistivity of nichrome is high and its resistance decreases with increase in temperature.
- (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
- (B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
- (C) Assertion (A) is true, but Reason (R) is false.
- (D) Assertion (A) is false, but Reason (R) is true.
Previously asked in CBSE board exam
2025 31/2/1 Q19
Generated by claude-sonnet-4-6 · 2026-06-15 06:43 · grounding rag
Model Answer
(C) Assertion (A) is true, but Reason (R) is false.
Assertion is correct — nichrome's high resistivity and high melting point make it suitable for heating devices. However, the Reason is false: the resistance of nichrome (and alloys in general) increases with increase in temperature, not decreases.
Source: Chapter 11, Section 11.5
---
Explanation
- The Assertion is directly supported by the textbook: alloys like nichrome have high resistivity and do not oxidise at high temperatures, so they are used in electric irons, toasters, etc.
- The Reason contains one correct part (high resistivity) but one wrong part: for metallic conductors and alloys, resistance increases with temperature. The textbook states "Both the resistance and resistivity of a material vary with temperature" — for metals/alloys this variation is an increase.
- Since the Reason is partially false (the key claim about resistance decreasing is wrong), option (C) is correct.
If a question refers to an image, map, graph or diagram that is not shown here, find the actual CBSE question paper on the CBSE website:
cbse.gov.in.