CHAPTER 18 ELECTRIC FORCES AND ELECTRIC FIELDS
Problems that are not marked with a star are considered the easiest to solve. Problems that are marked with a single star
are more difficult, whilt
those marked with a double star
are the most difficult.
Note to Instructors: Most ofthe homework problems in this chapter are available for assignment via an online homework management program such as
or WebAssign, and those marked with the icon
are presented in
using a guided tutorial format that provides enhanced
interactivity. See Preface for additional details.
ssm Solution is in the Student Solutions Manual.
This icon represents a biomedical application.
Solution is available online at www.wiley.comlcollegelcutnell
The Origin of Electricity,
Charged Objects and the Electric Force,
Conductors and Insulators,
Charging by Contact and by Induction
metal sphere has a charge of +8.0
What is the net
charge after 6.0
electrons have been placed on it?
2. Iron atoms have been detected in the sun's outer atmosphere,
some with many of their electrons stripped away. What is the net
electric charge (in coulombs) of an iron atom with 26 protons and
7 electrons? Be sure to include the algebraic sign (+ or
-) in your
3. Four identical metallic objects carry the following charges:
+6.2, -4.8, and -9.4 p,c. The objects are brought simultaneously
into contact, so that each touches the others. Then they are separated.
(a) What is the final charge on each object?
How many elec-
trons (or protons) make up the final charge on each object?
A plate carries a charge of -3.0
while a rod carries a
charge of +2.0
How many electrons must be transferred from
the plate to the rod, so that both objects have the same charge?
5. ssm Consider three identical metal spheres, A, B, and C. Sphere
carries a charge of
Sphere B carries a charge of
C carries no net charge. Spheres
and B are touched together and
then separated. Sphere C is then touched to sphere
from it. Last, sphere C is touched to sphere B and separated from it.
(a) How much charge ends up on sphere C?
What is the total charge
on the three spheres
(b) before they are allowed to touch each other
(c) after they have touched?
.•Four identical metal spheres have charges of
(a) Two of
the spheres are brought together so they touch, and then they are sep-
arated. Which spheres are they, if the final charge on each one is
(b) In a similar manner, which three spheres are brought
together and then separated, if the final charge on each of the three is
(c) The final charge on each of the three separated
spheres in part (b) is +3.0 p,c. How many electrons would have to