Question

Three charges $2q,-q$ and $-q$ are located at the vertices of an equilateral triangle. At the centre of the triangle:

• A. the field is zero but potential is non-zero
• B. the field is non-zero, but potential is zero
• C. both field and potential are zero
• D. both field and potential are non-zero

Answer 1

Answer: (B)

the field is non-zero, but potential is zero

For equilateral triangle the distances of each charges from centre are equal i.e, $r$ (say)
As potential is scalar quantity so potential at centre will be $V=\frac{1}{4\pi {ϵ}_0}[\frac{2q}{r}+\frac{-q}{r}+\frac{-q}{r}]=0$
As electric field is a vector quantity so net field at the centre has some non zero component.