A charge 'q' of opposite nature is revolving round an infinitely long linear charge of density `lambda` C/m in a circular orbit of radius 'r'.The speed of the revolving charge will be

Options

A. `sqrt(kqlamda//m)`
B. `kq//lamdam`
C. `sqrt((lamdaq//2piepsilon_(0)m))`
D. `kq//lamdamr`

Answer

C

Explanation

Contripital force on revolving `e^(-)`
`F_(c)=F_("electrod")`
`(mv^(2))/r=(qlamda)/(2piepsilon_(0)r)=qE`
On solving we get `v=sqrt((qlamda)/(2piepsilonm))`