Verified Solution • 2025–26 Session moderate

QPages 121-124: Q66: HC Verma: Concepts of Physics - Volume 2 Electric Field Potential Pages 121-124: Q66 Solution: How much work has to be done in assembling three charged…

⚠️ Common Exam Traps & Conceptual Pitfalls

Students often incorrectly multiply the single-pair potential energy by the number of charges ($3$) instead of the number of unique pairs, or forget that the total potential energy is the sum of all distinct pairwise interactions. For three charges, there are exactly three unique pairs (AB, BC, CA), so the total work is $3 \times \frac{kq^2}{l}$, not derived from a generic formula for $N$ charges without verifying the pair count.

How much work has to be done in assembling three charged particles at the vertices of an equilateral triangle, as shown in the figure?

Step-by-Step Verified Solution

**Answer:**

W = \frac{3kq^2}{l}

. **STEP-BY-STEP Explanation:** Three charges

q

at vertices of equilateral triangle of side

l

. Work done = potential energy of system:

U = 3 \times \frac{kq^2}{l}

All Questions in this Chapter

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