Verified Solution • 2025–26 Session moderate

QPages 198-203: Q9: HC Verma: Concepts of Physics - Volume 2 Electric Current in Conductors Pages 198-203: Q9 Solution: What length of a copper wire of cross-sectional area will be…

⚠️ Common Exam Traps & Conceptual Pitfalls

Students frequently fail to convert the cross-sectional area from $\text{mm}^2$ to $\text{m}^2$ correctly, often using $10^{-3}$ instead of the correct $10^{-6}$ factor, which leads to a length error of three orders of magnitude. Always verify that $1 \text{ mm}^2 = 10^{-6} \text{ m}^2$ before substituting into the resistance formula $R = \rho l / A$.

What length of a copper wire of cross-sectional area

0.01 \text{ mm}^2

will be needed to prepare a resistance of

1 \text{ k}\Omega

? Resistivity of copper =

1.7 \times 10^{-8} \ \Omega\text{m}

.

Step-by-Step Verified Solution

**Answer:**

l = 0.6

km. **Step-by-Step Explanation:** Given:

A = 0.01

mm_

= 10^{-8}

m_,

R = 1000\\ \\Omega

,

\\rho_{Cu} = 1.7 \\times 10^{-8}\\ \\Omega\\text{m}

.

l = \\frac{RA}{\\rho} = \\frac{1000 \\times 10^{-8}}{1.7 \\times 10^{-8}} = 588

m

\\approx 0.6

km [citation:4][citation:6][citation:9].

All Questions in this Chapter

QPage 196: Q1 QPage 196: Q2 QPage 196: Q3 QPage 196: Q4 QPage 196: Q5 QPage 196: Q6 QPage 196: Q7 QPage 196: Q8 QPage 196: Q9 QPage 196: Q10 QPage 196: Q11 QPage 196: Q12 QPage 196: Q13 QPage 196: Q14 QPage 196: Q15 QPage 196: Q16 QPage 196: Q17 QPages 196-197: Q1 QPages 196-197: Q2 QPages 196-197: Q3 QPages 196-197: Q4 QPages 196-197: Q5 QPages 196-197: Q6 QPages 196-197: Q7 QPages 196-197: Q8 QPages 196-197: Q9 QPages 196-197: Q10 QPages 196-197: Q11 QPages 196-197: Q12 QPages 196-197: Q13 QPages 196-197: Q14 QPages 196-197: Q15 QPages 196-197: Q16 QPages 197-198: Q1 QPages 197-198: Q2 QPages 197-198: Q3 QPages 197-198: Q4 QPages 197-198: Q5 QPages 197-198: Q6 QPages 197-198: Q7 QPages 197-198: Q8 QPages 197-198: Q9 QPages 198-203: Q1 QPages 198-203: Q2 QPages 198-203: Q3 QPages 198-203: Q4 QPages 198-203: Q5 QPages 198-203: Q6 QPages 198-203: Q7 QPages 198-203: Q8 QPages 198-203: Q9 QPages 198-203: Q10 QPages 198-203: Q11 QPages 198-203: Q12 QPages 198-203: Q13 QPages 198-203: Q14 QPages 198-203: Q15 QPages 198-203: Q16 QPages 198-203: Q17 QPages 198-203: Q18 QPages 198-203: Q19 QPages 198-203: Q20 QPages 198-203: Q21 QPages 198-203: Q22 QPages 198-203: Q23 QPages 198-203: Q24 QPages 198-203: Q25 QPages 198-203: Q26 QPages 198-203: Q27 QPages 198-203: Q28 QPages 198-203: Q29 QPages 198-203: Q30 QPages 198-203: Q31 QPages 198-203: Q32 QPages 198-203: Q33 QPages 198-203: Q34 QPages 198-203: Q35 QPages 198-203: Q36 QPages 198-203: Q37 QPages 198-203: Q38 QPages 198-203: Q39 QPages 198-203: Q40 QPages 198-203: Q41 QPages 198-203: Q42 QPages 198-203: Q43 QPages 198-203: Q44 QPages 198-203: Q45 QPages 198-203: Q46 QPages 198-203: Q47 QPages 198-203: Q48 QPages 198-203: Q49 QPages 198-203: Q50 QPages 198-203: Q51 QPages 198-203: Q52 QPages 198-203: Q53 QPages 198-203: Q54 QPages 198-203: Q55 QPages 198-203: Q56 QPages 198-203: Q57 QPages 198-203: Q58 QPages 198-203: Q59 QPages 198-203: Q60 QPages 198-203: Q61 QPages 198-203: Q62 QPages 198-203: Q63 QPages 198-203: Q64 QPages 198-203: Q65 QPages 198-203: Q66 QPages 198-203: Q67 QPages 198-203: Q68 QPages 198-203: Q69 QPages 198-203: Q70 QPages 198-203: Q71 QPages 198-203: Q72 QPages 198-203: Q73 QPages 198-203: Q74 QPages 198-203: Q75 QPages 198-203: Q76 QPages 198-203: Q77 QPages 198-203: Q78 QPages 198-203: Q79 QPages 198-203: Q80 QPages 198-203: Q81 QPages 198-203: Q82 QPages 198-203: Q83 QPages 198-203: Q84

Related Learning Resources & Exam Preparation

Chapter Practice Bank

Practice all topic-wise questions from Electric Current in Conductors

Reference Textbook Solutions

Explore complete chapter exercises for HC Verma: Concepts of Physics - Volume 2

Competitive PYQ Question Bank

Browse year-wise authentic previous years' questions with solutions

Authentic CBT Mock Tests

Simulate official exam environment with live timer and percentile scoring