Three point charges Q, 2Q and 8Q are to be placed on a 10 cm long straight line. Find the position where the charges should be placed such that the potential energy of this system is minimum. In this situation, what is the electric field at the position of the charge Q due to the other two charges?
Text Solution
Verified by ExpertsCHECK THE SOLUTION.
Q at a distance of 
cm from 2Q between 2Q and 8Q, E = 0.
Sol. For potential energy of this system to be minimum, point charges 2Q & 8Q must be placed at the end positions of straight line. So that the mutual energy should be minified
PE = 
+ 
+ 
For minimum PE of system
= 0
⇒ – 
+ 
= 0
⇒ (10 – x) 2 = 4x 2 ⇒ 10 – x = ± 2x
⇒ x = 
cm (from 2q charge)
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