Three charges +3, +q and Q are placed on a straight line with equal separation. In order to make the net force on q zero, the value of Q will be:
Correct answer: A. 3q
- A. 3q
- B. 2q
- C. 4q
- D. 5q
Explanation
Using Coulomb's law,F = kq1q2/r2In order to make the net force on q 0, both +3 and Q shall exert equal forces.Or For +3 on q = F of Q on qkq1aq2a/r2 = kq1bq2b/r2q1aq2a = q1bq2bBut here, one charge is common, let's say, q2a = q2b = qq.q1a = q. q1bq1a = q1bAs q1a = +3,q1b = 3Hence, option A is the correct option.
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