Question

Three point charges q1 q2 and q3 are in line at equal distances

Answer 1

Can you complete the question fully?

Answer 2

:Three point charges q1, q2, q3 are in line at equal distances. q2 and q3 are opposite in sign. Find the magnitude and sign of q1, if net force on q3 is zero

Let Q1 be a test positive charge, since charges of Q2 and Q3 are opposite in sign, there exists an attractive force between them. One point to be kept in mind here is that the net force on Q3 must be 0 as given in the problem. In order to keep force on Q3 be 0, the force between Q1 and Q3 must be force of repulsion as we already have attractive force between Q2 and Q3

Now to satisfy the equilibrium position, the two forces must balance each other.

KQ1Q3/4R2 = -KQ2Q3/R2….. (distance between Q1 and Q3 is 2R).

Q1 = -4Q2

Hence charge of Q1 is opposite to that of Q2 and same as that of Q3