Question

1) a conducting sphere is charged up such that the voltage on its surface is 100V (relative to infinity) If the sphere's radius were twice as large, but the charge on the sphere did not change, the voltage on the surface would be??

is it 50 V ?

2) If an isolated solid metal sphere contains an excess charge of +25 µC, the potential at the surface of this sphere is higher than the potential at its center.True or False?

I said True??


3) If an object is at zero potential, it must be uncharged?? True or False

False??

4) If the potential along the z-axis is directly proportional to the distance z along that axis, then the z component of the electric field must be constant along the z-axis. True or False???

True??


5) If the electrical potential is 100V at 1.0 cm from a point charge, the potential will be 25 V if you go twice as far away...True or False??

False.???

Answer 1

50 V seems right
Conductor at same potential throughout
Zero potential ok for charged object, such as other plate of capacitor
V = kz E = dV/dz = k = constant
If point charge is only charge in the situation, V proportional to 1/r

Answer 2

b) seems to be rigth since potential inside a closed conductor is zero.

Answer 3

C) look like false as we see in b)