Download HW10 - University of St. Thomas

Physics 112 HW10/5
Due Wednesday, 1 October 2014
U3-VfEI07. A spherical conducting shell has an inner radius of 3 cm and an outer radius of 5
cm. It carries a total charge of 3 nC. A second, larger spherical conducting shell has an inner
radius of 8 cm and an outer radius of 10 cm. It carries a total charge of -5 nC, and is concentric
with the first (the first is inside the second). Assuming that the electric potential goes to zero
as we get very far away from the concentric shells, find and graph the electric potential as a
function of distance r from their common center (all r > 0).
U3-VfEI05. A long coaxial cable consists of a 2.0-mm-diameter inner conductor and an outer
conductor of diameter 1.6 cm and negligible thickness (see Fig. 22.22 in text). If the inner and
outer conductor have effective linear charge densities of -56 nC/m and +56 nC/m, respectively,
what is the magnitude of the potential difference between them?
U3-VfEI06. Two conducting spheres are isolated from each other and other charges. The larger
sphere has a radius of 30 cm, while the smaller sphere has a radius of 1 mm. They are both
charged up to a voltage of +500V (with respect to ground, which is V = 0 as r  ). Determine
the surface charge density (in C/m2) of each sphere. Which one has the greater surface charge
density?
U3-EfV01. (Wolfson, Ch. 22 Problem 30) The figure at
right shows some equipotentials in the x-y plane.
a) In what region is the electric field the strongest?
b) What is the direction of the field where it is the
strongest?
c) What is the magnitude of the field where it is the
strongest?
(over)
U3-EfV02. For the situation below, the black areas are conductive like the tape and ink in our
equipotential lines lab. Sketch four equipotential lines between these two conductive shapes
if there is a 12 volt potential difference between them. Also sketch the electric field lines.
-6V
+6V
(over)