Introductory Physics Volume Two

34 Electric Field 1.8
A charged ball of mass 1.00 g is suspended on a light string in the
presence of a uniform electric field as shown. When ⃗ E = (3.00î +
5.00ĵ) × 10 5 N/C, the ball is in equilibrium at θ = 37.0 ◦ .
(a) Find the charge on the ball.
(b) Find the tension in the string.
⊲ Problem 1.21
A triangular box is in a horizontal electric field of magnitude E =
7.8 × 10 4 N/C as shown
30 cm
10 cm 60°
E
(a) Compute the electric flux through each face of the box.
(b) Compute the net electric flux through the entire surface of the box.
⊲ Problem 1.22
The nose cone of a rocket is in a uniform electric field of magnitude E 0
as shown.
E
E
It is parabolic in cross section, of length d and of radius r. Compute
the electric flux through the paraboloidal surface.
⊲ Problem 1.23
A charge Q is at the center of a cube of side L.
(a) Find the flux through each face of the cube.
(b) Find the flux through the entire surface of the cube.
(c) Would these answers change if the charge was not at the center?
⊲ Problem 1.24
A charge Q is located just above the center of the flat face of a solid
hemisphere of radius R.
(a) What is the electric flux through the curved surface.
(b) What is the electric flux through the flat surface.
⊲ Problem 1.25
Find the electric field at the origin if there is a charged rod that goes
from x = a to x = b assuming that the charge density of the rod is
λ = cx n .
d