Two identical metallic sphere's A and B having charges ` +4 Q and -10 Q ` are kept a certain distance apart. A third identical uncharged sphere C is first placed in contact with sphere A and then with sphere B. Spheres A and B are then brought in contact and then separated. Find the charges on the spheres A and B.

Explanation

Initial charge on sphere `A, q_A = +4Q and "charges" on B , q_B = - 10Q .` When an identical uncharged sphere C is placed in contact with sphere A , it shares its charge and charge on `C, q_C =(q_A)/( 2)= +(4Q)/( 2) ` =2Q and the remaining charge on A becomes `q_A =+2Q `
Now sphere C having charge `q_C =+2Q ` is brought in contact with sphere B having charge `q_B = -10 Q `. The two spheres share their charges and acquire charges
` " " q_C. =q_B. =((+2Q-10Q))/(2) =-4Q`
Now finally spheres A ( charges `q_A. =+2Q) ` and B (charges `q_B. =-4Q ) ` are brought in contact and then separated. On contact A and B share their charges equally and final value of charge on A or B will be ` " " q_A.. " " q_B.. =(+2Q-4Q)/( 2) = -Q `