Two point charges q_1=3μ C and q_2=-4μ C are placed at points (2 i+3 j+3 k) and ( i+ j+ k) respectively. Force on charge q_2 is N. ( Take 1 4πε_0 =…
JEE Main 2026 — Physics Electromagnetism
2026mcqmedium
Two point charges q1=3μC and q2=−4μC are placed at points (2i^+3j^+3k^) and (i^+j^+k^) respectively. Force on charge q2 is ________ N. (Take 4πϵ01=9×109 SI Units)
Official previous-year question
Held on 8 Apr 2026 · Verified 6 Jul 2026.
Options
A
(12i^+24j^+24k^)×10−3
B
(4i^+8j^+8k^)×10−3
C
(3i^+6j^+6k^)×10−3
D
(−4i^−8j^−8k^)×10−3
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Solution
Position vector of q1, r1=2i^+3j^+3k^
Position vector of q2, r2=i^+j^+k^
Vector from q1 to q2 is r21=r2−r1=(i^+j^+k^)−(2i^+3j^+3k^)=−i^−2j^−2k^
Magnitude ∣r21∣=(−1)2+(−2)2+(−2)2=9=3
Force on q2 due to q1 is given by Coulomb's law in vector form:
F21=4πϵ01∣r21∣3q1q2r21
Substituting the given values:
F21=339×109×(3×10−6)×(−4×10−6)(−i^−2j^−2k^)
F21=27−108×10−3(−i^−2j^−2k^)
F21=−4×10−3(−i^−2j^−2k^)
F21=(4i^+8j^+8k^)×10−3 N
Answer: (4i^+8j^+8k^)×10−3
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