Two identical metal spheres with +12 `muC and -8 muC` are kept at certain distance in air . They are brought into contact and then kept at the same distance . The ratio of the magnitudes of electrostatic forces between them before and after contact is

Options

A. `24 : 1`
B. `4 : 1`
C. `12 : 1`
D. `8 : 1`

Answer

A

Explanation

Perhaps by a printing error , the charges are given in this problem as `12muFand-8muF` instead of `12muCand-8muC`.

Force `F_(1)=-(1)/(4piepsilon_(0))*((12xx10^(-6)xx8xx10^(-6)))/(d^(2))`

`thereforeF_(2)=+(1)/(4piepsilon_(0))*((2xx10^(-6)xx2xx10^(-6)))/(d^(2)`
`therefore(F_(1))/(F_(2))=(96)/(4)=(24)/(1)`.