Answer:
a)
*The charges of which and the cube are of the same sign..
Q_exterior = 3 Q
* the charge of the sphere has a different sign than the charge of the cube,
Q_exterior = Q
b) Q = 0
Explanation:
To correctly describe this experiment, you must remember that in metals charges are mobile and that charges of the same sign repel and of different signs attract.
Let's analyze each situation
a) Suppose that the charges of which and the cube are of the same sign.
When the ball is introduced without touching the walls, its charge Q attracts a charge of equal magnitude and different sign to the internal wall. If we create a Gaussian surface around the inner wall of the sphere the net charge between the ball and the inner wall is zero. Consequently, a face Q should have been generated in the outer wall, therefore in this wall it has a total load of
Q_exterior = 3 Q
Now suppose that the charge of the sphere has a different sign than the charge of the cube, for simplicity let's say that the charge of the sphere is -Q and the cube + 2Q,
Again we create a Gaussian surface outside the inner wall, now the charge on the ball attracts a charge of value + Q to neutralize the charge between the ball and the inner wall. Therefore a load remains on the outer wall
Q_exterior = + Q
b) The cube is connected to earth and it is touched with the ball, in this case the charge of the two bodies is neutralized by the Earth, therefore the bodies have zero charge
Q = 0
