(Hint: According to a version of the shell theorem, the force exerted by a spherically symmetric charge distribution on a test
charge at any external point is the same as if all the charge were concentrated at its center.) (b) What is the potential differnce
between a location 500 m above the surface of the planet and a location at ground level?
(a) N/C
(b) V7.4 A certain 4.8-volt cellular telephone battery has a capacity of 600 mAh. (One mAh equals 3.6 coulombs.) When the battery's
charge is too low to run the phone any longer (assume it is zero), the battery must be recharged. (a) How much work is done
by the recharger? (b) If electricity costs you 9.0 cents per kWh, how much does one recharge cost you?
(a) J
(b) $7.5 A charged particle of mass 8.39×10í^4 kg starts from rest and accelerates through a potential difference of +25,000 V to reach
a speed of 1.26e+3 m/s. What is the charge on this particle?
C
Section 10 - Equipotential surfaces
10.1 A point charge of 8.40 mC is surrounded by an equipotential surface with a radius of 0.298 m. What is the electric potential
on the surface?
V10.2 What is the radius of the 2.5×10í^9 V equipotential surface that surrounds an isolated proton?
m10.3 A positive point charge is surrounded by two equipotential surfaces. (a) What is the shape of the surfaces? (b) On which of
the surfaces is the electric potential greater? (c) If the larger of the surfaces has 10 times the area of the smaller, what is the
ratio of the potential on the larger to the potential on the smaller?
(a) i. Cube
ii. Pyramid
iii. Sphere
(b) i. The surface closer to the point charge
ii. The surface farther from the point charge
(c)Section 11 - Electric potential and a uniform electric field
11.1 A uniform electric field of 2.0×10^5 N/C is oriented in the negative x direction. How much work must be done to move an
electron 3.0 m in the positive x direction, if it begins and ends at rest?
J
11.2 In a typical television or in an older computer picture tube (CRT), the electrons that strike the screen to form an image are
accelerated between two charged plates that have a potential difference of 2.5×10^4 V. The plates are separated by a distance
of 1.3 cm. Assuming that there is a uniform electric field between the plates, calculate the strength of the field.
N/C11.3 Points 1 and 2 are located in a uniform electric
field of strength 325 N/C. The displacement
vector from point 1 to point 2 points in the
same direction as the field, and has a length of
15.4 cm. The electric potential at point 1 is
9.15 V. What is the potential at point 2?
V
11.4 Starting at a point in a uniform electric field of strength 9.50 N/C, how far and in what direction (relative to the field) must one
travel to experience an increase in potential of 13.6 V?
m i. In the direction of the field
ii. Opposite the direction of the field
iii. Perpendicular to the field