Two idential point charges Q are kept at a distance r from each other. A third point charge is placed on the line joing the above two charges such that all the three charges are in equilibrium. The third charge
(a) should be of magnitude q=………..
(b) should be of sign .......
(c ) should be placed ........ .

Explanation

To solve the problem of finding the third charge \( q \) that will keep the system of three charges in equilibrium, we can follow these steps:

### Step 1: Understand the Configuration
We have two identical point charges \( Q \) placed at a distance \( r \) apart. A third charge \( q \) is to be placed on the line joining these two charges such that the net force on each charge is zero.

### Step 2: Position of the Third Charge
Let’s denote the position of the third charge \( q \) as \( x \) from the first charge \( Q \). Consequently, the distance from the second charge \( Q \) will be \( r - x \).

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