Consider three identical metal spheres, A, B, and C. Sphere A carries a charge o
ID: 251015 • Letter: C
Question
Consider three identical metal spheres, A, B, and C. Sphere A carries a charge of +6q. Sphere B carries a charge of -q. 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. Lastly, sphere C is touched to sphere B and separated from it. (a) What is the ratio of the final charge on sphere C to q? What is the ratio of the final total charge on the three spheres to q (b) before they are allowed to touch each other and (c) after they have touched?
Explanation / Answer
At first charges are distributed like this
A = +6q, B = -q, C = 0
Then you touch A and B => 6q - q = 5q
The charge is equally distributed over both spheres so you end up with
A = -2.5q, B = -2.5q, C = 0
Next you touch C to A
-2.5q + 0 = -2.5q
A = -1.25q, B = -2.5q, C = -1.25q
Then C is touched to B
-1.25q -2.5q = -3.75q
A = -1.25q, B = -1.875q, C = -1.875q