Q1. [2] § 11.4 OHM'S LAW § 11.5 FACTORS ON WHICH THE RESISTANCE OF A CONDUCTOR DEPENDS § 11.6 RESISTANCE OF A SYSTEM OF RESISTORS
V–I graph for two conducting wires A and B are as shown. If both wires are of the same length and same diameter, which of the two is made of a material of high resistivity ? Give reasons to justify your answer.
Previously asked in CBSE board exam
2023 31/2/1 Q25
Generated by claude-sonnet-4-6 · 2026-06-15 06:44 · grounding rag
Model Answer
Wire B is made of a material of higher resistivity.
Reason: From the V–I graph, the slope (V/I) gives resistance. Wire B has a steeper slope, meaning higher resistance. Since both wires have the same length and same diameter (same cross-sectional area), and using $R = \rho \dfrac{l}{A}$, a higher resistance means higher resistivity ($\rho$).
Source: Chapter 11 – Electricity, Section 11.5 Factors on which the resistance of a conductor depends
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Explanation
- The key formula is $R = \rho \dfrac{l}{A}$. Since $l$ and $A$ are the same for both wires, $R \propto \rho$.
- On a V–I graph, slope = V/I = R. A steeper line → higher R → higher ρ.
- Examiners expect you to: (1) identify wire B, (2) state that slope gives resistance, and (3) link it to resistivity via the formula. All three points together earn full 2 marks.
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