A ring of charge with radius `0.5m` has `0.002 pi` m gap. If the ribg carries a charge of `+1 C` the electric field at the center is

Options

A. `7.5xx10^(7)NC^(-1)`
B. `7.2xx10^(7)NC^(-1)`
C. `6.2xx10^(7)NC^(-1)`
D. `6.5xx10^(7)NC^(-1)`

Answer

B

Explanation

Change on the element opposite to the gap is
`dq=(Q)/(2 pi r)(0.002 pi)`
`=(1)/(2 pi(0.5))==(2 pi)/(1000)=2xx10^(-3)C`
`E=(9xx10^(9)xx2xx10^(-3))/((0.5)^(2))=7.2xx10^(7)NC^(-1)`