Question

A non conducting ring of radius R has uniformly distributed positive charge. A small part of the ring, of length d, is removed (d << R). The electric field at the centre of the ring will now be –

• A. Directed towards the gap, inversely proportional to R³
• B. Directed towards the gap, inversely proportional to R²
• C. Directed away from the gap, inversely proportional to R³
• D. Directed away from the gap, inversely proportional to R²

Answer 1

Answer: (A)

Directed towards the gap, inversely proportional to R³

Answer 2

Charge on section removed dQ = $\frac { \mathrm { Qd } } { 2 \pi \mathrm { R } }$

\ E = $\frac { \mathrm { KdQ } } { \mathrm { R } ^ { 2 } }$ = K $\frac { \mathrm { Qd } } { 2 \pi \mathrm { R } ^ { 3 } }$