Electrostatics Question 193

Question: Two point charges $ +3\mu C $ and $ +8\mu C $ repel each other with a force of $ 40N $ . If a charge of $ -5\mu C $ is added to each of them, then the force between them will become [SCRA 1998; JIPMER 2000]

Options:

A) $ -10N $

B) $ +10N $

C) $ +20N $

D) $ -20N $

Show Answer

Answer:

Correct Answer: A

Solution:

In second case, charges will be $ -2\mu C $ and $ +3\mu C $

Since $ F\propto Q _{1}Q _{2} $ i.e. $ \frac{F}{{{F}’}}=\frac{Q _{1}Q _{2}}{Q{’ _{1}}Q{’ _{2}}} $ $ \frac{40}{{{F}’}}=\frac{3\times 8}{-2\times 3}=-4 $

therefore $ {F}’=10N $ (Attractive)



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