Question

Three charges $Q,2Q,8Q$ are to be placed along a line whose length is $R.$ The positions where these charges should be placed respectively such that the potential energy of the system is minimum are

• A. $\frac{R}{3},O,R$
• B. $\frac{2R}{3},R,O$
• C. $R,O,\frac{2R}{3}$
• D. $O,\frac{R}{3},R$

Answer 1

The correct option is D $O,\frac{R}{3},R$

Three charges $Q,2Q,8Q$

length $=R$

the system is minimum $0,\frac{R}{3},R$

$0<\frac{R}{3}<R$

because,

the smallest distance from the $Q$ will be $0$ then $\frac{R}{3}$ then $R$.