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Two point charges $q_1$ and $q_2$ are ' $l$ ' distance apart. If one of the charges is doubled and the distance between them is halved, the magnitude of force becomes $n$ times, where $n$ is
PhysicsElectrostaticsMHT CETMHT CET 2022 (05 Aug Shift 1)
Options:
  • A $8$
  • B $1$
  • C $2$
  • D $16$
Solution:
2256 Upvotes Verified Answer
The correct answer is: $8$
The correct option is (A)
Concept: Functional dependence of Coulombic Force on charges $\left(q_1, q_2\right)$ separated with distance $l$ is given by
$F \propto \frac{q_1 q_2}{l^2}$
Therefore, if one of the charges is doubled and the distance between them is halved, the magnitude of new force
$F_{\text {new }} \propto\left\{\frac{2 q_1 q_2}{\left(\frac{l}{2}\right)^2}\right\}$
So, $F_{\text {new }}=8 F$.

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