Question

A particle of mass m carrying a charge `-q_(1)` starts moving around a fixed charge `+q_(2)` along a circular path of radius r. Find the time period of revolution T of charge `-q_(1)`.

Answer 1

Electrostatic force on `-q_(1)` to `+q_(2)`will provide the necessary centripetal force
hence `(Kq_(1)q_(2))/(r^(2))=(mv^(2))/(r),v=sqrt((Kq_(1)q_(2))/(mr))`
`T=(2pir)/(v)=sqrt((16pi^(3)epsilon_(0)mr^(3))/(q_(1)q_(2)))`