Consider three identical metal spheres, A, B, and C. Sphere A carries a charge o
ID: 3279872 • Letter: C
Question
Consider three identical metal spheres, A, B, and C. Sphere A carries a charge of -8q. Sphere B carries a charge of -3q. Sphere C carries no net charge. Spheres A and B are touched together and then separated. Sphere C is then touched to sphere A and separated from it. Last, sphere C is touched to sphere B and separated from it. For the following questions, express your answers in terms of q.
(a) How much charge ends up on sphere C?
(b) What is the total charge on the three spheres before they are allowed to touch each other?
(c) What is the total charge on the three spheres after they have touched?
Explanation / Answer
Charges get added on being touched and may also neutralise when equal
On touching A,B total charge becomes -11q, now as A,B are identical, each has -5.5q charge.
Again, A,C are touched so, charge on either becomes -2.75q. as C was neutral and A,C are identical.
C,B are touched so total charge becomes 2.75+5.5 =8.25q.
Therefore on both B,C charge will be -4.125q.
(a). -4.125q
(b) total charge on all spheres was -11q.
(c) total charge after touching each other = -4.125×2 -2.75 = -8.25 -2.75 = -11q
hence, charge remains conserved.