Answer to Question #184168 in Electricity and Magnetism for Niall Rio

Question

Spheres A, B, and C have charges +8.0 C, +12.0 C, and -5.0 C, respectively. Spheres A and B touched each other and then separated. Sphere A then touched sphere C and then separated. What is the final charge on each sphere assuming that r_A = r_B = 2r_C?

Answer 1

$q_B'=\frac{q_A+q_B}{2}=+10.0~C,$

$\frac qr=const,$

$q'_A=\frac{\frac{q_A+q_B}{2}+q_C}{1+2}=+1.7~C,$

$q_C'=\frac{2(\frac{q_A+q_B}{2}+q_C)}{1+2}=+3.3~C.$