The force of repulsion between two charges +1 and 6C is 12N. A third charge -4C add between them, now the force between them will be …

Options

A. 4 N repulsive
B. 4 N attractive
C. 8 N repulsive
D. 8 N attractive

Answer

B

Explanation

Here, `F = (kq_(1)q_(2))/r^(2)`
`F_(1) = (k(2)(6))/gamma^(2)` and `F_(2) = (k(-2)(2))/r^(2)`
`therefore F_(1) = (12k)/gamma^(2)`…….(i), `therefore F_(2) = (-4k)/r^(2)`……….(ii)
`therefore F_(2)/F_(1) = -4/12 = -1/3 F_(2)` is a force between t after addint `-4C` charge.
`therefore q_(1)^(.) = -2C` and `q_(2)^(.) = 2C`
`therefore F_(2) = -1/3 xx F_(1) =-1/3 xx 12 = -4 N`
Negative sign indicates attractive force.