Two insulated identically sized charged copper spheres A and B have their centers separated by a distance of 50 cm.` q= 6.5 xx 10^(-7)C `. A third sphere of the same size but uncharged is brought in contact with the first, then brought in contact with the second, and finally removed from both. What is the new force of repulsion between A and B?

Explanation

Charge on each of the spheres A and B is `q=6.5 xx 10^(-2)C`
When a similar but unchargod sphoro C is placed in contact with sphere A, cach sphere shares a change `q/2` equally.
Now when tho sphere C `("with charge "q/2)` is placed in contact with sphere B (with charge q). the charge is redistributed equally, so that charge on sphore B or `C=1/2 (q+q/2)=3/4 q`

`F=(9 xx 10^(9) xx q_(A) q_(B))/(r^(2)) =(9 xx 10^(9) xx (q/2) 3/4)/(r^(2))=3/8 xx F_(1)=3/8 xx 1.5 xx 10^(-2) =5.7 xx 10^(-2)N`