A wheel having mass m has charges + q and - q on diametrically opposite points. It remains in equilibrium on a rough inclined plane in the presence of a vertical electric field E. Then value of E is ......

Options

A. `(mg tan theta)/(q)`
B. `(mg)/(q) `
C. `(mg)/(2q)`
D. `(mg tan theta)/(2q)`

Answer

B

Explanation

For equilibrium of wheel `vecF_(G)= vecF_(E)`
`vecrxx vecF_(G)= vectau`
`r F_(G) "sin" theta ` = p E sin `theta`
rms sin `theta= pE sin theta rarr` where p = 2 r q
`:. E = (mg)/(2q)`