COMEDK2018PhysicsElectrostatics
The charges Q,+q and +q are placed at the vertices of an equilateral triangle of side l . If the net electrostatic potential energy of the system is zero, then Q is equal to
Options
- A-q / 2
- B-q
- C+q / 2
- DZero
Correct answer
A. -q / 2
Step-by-step solution
The given situation is shown below Net potential energy of the system =0 aligned & i.e. U_ net =0 & 1 4 ₀ q₁ q₂ l + 1 4 ₀ q₂ q₃ l + 1 4 ₀ q₃ q₁ l =0 aligned q₁ q₂+q₂ q₃+q₃ q₁=0 Q q+q q+q Q=0 2 Q q+q²=0 q(2 Q+q)=0 Since, q 0 2 Q+q=0 Q= -q 2