Question

Two point charges of + 3 $\mu C$and + 4 $\mu C$ repel each other with a force of 10 N. If each is given an additional charge of $- 6\mu C,$ the new force is.

• A. 2N
• B. 4N
• C. 5N
• D. 7.5 N

Answer 1

Answer: (D)

7.5 N

Answer 2

: Here, $q_{1} = + 3\mu C,q_{2} = + 4\mu C,F = 10N$

$q_{1}' = + 3 - 6 = - 3\mu C$

$q_{2}' = + 4 - 6 = - 2\mu C,$

$= \frac{( - 3) \times ( - 2)}{2 \times 6} = \frac{6}{8} = \frac{3}{4}\therefore F' = \frac{3}{4} \times F = \frac{3}{4} \times 10 = 7.5N$