In fig. a central particle of charge `-q` is surrounded by two circular rings of charged particle of radii r and R, with Rgtr. what is the magnitude and dirction of the net electrostatic force on the central particle due to the other particles?

Explanation

Net force on charge due to outer ring will be zero. Due to inner ring. The magnitude of force on `-q` at center is
`F_(n)=sqrt(F^(2)+F^(2))=sqrt(2)F=sqrt(2)xx(1)/(4 pi epsilon_(0))xx(2qxxq)/(r^(2))`
`=(q^(2))/(sqrt(2)pi epsilon_(0)r^(2))`
The direction is at angle `45^(@)` from the x-axis in second quardrant.