ADDITIONS TO WOLFSON PROBLEMS AND PROBLEMS FROM OTHER TEXTS
JULY 14  JULY 20
WOLFSON  CHAPTER 25
E3. This is the exercise accompanying Example 254 on page 639.
35. (b) Plot E(r) and V(r) from r = 0 to r = 4.0 m for
a = 0.5 m, b = 0.9 m, c = 1.0 m and Q = 1.0 microC.
Halliday and Resnick  2nd Ed  CHAPTER 26
19. A positive charge per unit length lambda is distributed
uniformly along a straightline segment of length L.
(a) Determine the potential (chosen to be zero at
infinity) at a point P a distance y from one end of
the charged segment and in line with it. (b) Use the
result of (a) to compute the component of the electric
field at P in the ydirection (along the line). (c)
Determine the component of the electric field at P in
a direction perpendicular to the straight line.
 . P


y


 + Figure for H 26:19
 +
 +
 + the line of plus marks
L + stands for the line of
 + positive charge
 +
 +
 +
20. On a thin rod of length L lying along the xaxis with one
end at the origin (x=0), there is distributed a positive
charge per unit length given by lambda = cx, where c is a
constant. (a) Taking the electrostatic potential at
infinity to be zero, find V at the point P on the yaxis.
(b) Determine the vertical component E_y of the electric
field at P from the result of part (a). (c) Why cannot
E_x, the horizontal component of the electric field at P,
be found using the result of part (a)?
y axis

 Figure for H 26:20
P is on the 
y axis, a . P
distance y 
from the  the line of plus marks
origin  stands for the line of
 positive charge

+++++++++++++++++++ x axis
(0,0)< L >


(P prefixes) HRW Problem Supplement #1  CHAPTER 25
58. Consider a flat, nonconducting ring of outer
radius R and inner radius r = 0.200R; the ring
has a uniform charge per unit area of sigma.
With V = 0 at infinity, find an expression for
the electric potential at point P on the central
axis of the ring, at a distance z = 2.00R from
the center of the ring.
(P prefixes) HRW Problem Supplement #1  CHAPTER 26
53. A certain parallelplate capacitor is filled with
a dielectric for which Kappa = 5.5. The area of
each plate is 0.034 m^2, and the plates are
separated by 2.0 mm. The capacitor will fail
(short out and burn up) if the electric field
between the plates exceeds 200 kN/C. What is the
maximum energy that can be stored in the capacitor?
66. Two parallelplate capacitors A and B are connected
in parallel across a 600 V battery. Each plate has
area 80.0 cm^2 and the plate separations are 3.0 mm.
Capacitor A is filled with air; capacitor B is
filled with a dielectric of dielectric constant
Kappa = 2.60. Find the magnitude of the electric
field within (a) the dielectric of capacitor B and
(b) the air of capacitor A. What are the free
charge densities sigma on the higherpotential
plate of (c) capacitor A and (d) capacitor B?
(e) What is the induced charge density sigma' on
the surface of the dielectric which is nearest to
the higherpotential plate of capacitor B.
Halliday and Resnick  2nd Ed  CHAPTER 27
7. Two metal objects, a saw and a wrench, are lying
sidebyside on an nonconducting table; the two
metal objects are not in contact with one another;
they have net charges of +70 pC and 70 pC, and
this results in a 20 V potential difference
between them. (a) What is the capacitance of the
system? (b) If the charges are changed to +200 pC
and 200 pC, what does the capacitance become?
(c) What does the potential difference become?
13. The figure for this problem is Fig. 2629, except
the width of the slab is now b instead of 0.6d.
A slab of copper of thickness b is thrust into a
parallelplate capacitor of plate area A; it is
exactly halfway between the plates. (a) What is
the capacitance after the slab is introduced?
(b) If a charge q is maintained on the plates, what
is the ratio of the stored energy before to that
after the slab is inserted? (c) How much work is
done on the slab as it is inserted? Is the slab
sucked in or must it be pushed in?
18. Two parallel plates of area 100 cm^2 are given charges
of equal magnitudes 0.89 microC but opposite signs.
The electric field within the dielectric material
filling the space between the plates is 1.4 MV/m.
(a) Calculate the dielectric constant of the material.
(b) Determine the magnitude of the charge induced on
each dielectric surface.
43. You are asked to construct a capacitor having a
capacitance near 1 nF and a breakdown potential in
excess of 10000 V. You think of using the sides of
a tall Pyrex drinking glass as a dielectric, lining
the inside and outside curved surfaces with aluminum
foil to act as the plates. The glass is 15 cm tall
with an inner radius of 3.6 cm and an outer radius
of 3.8 cm. What are the (a) capacitance and (b)
breakdown potential of this capacitor?
45. The figure for this problem is Fig. 2629, except
that the slab is a dielectric with kappa = 2.61
instead of a conductor, and a 85.5 V battery is
connected to the capacitor plates while the dielectric
is being inserted. The area A = 115 cm^2, d = 1.24 cm,
and the width of the slab is (0.629)d. Calculate
(a) the capacitance, (b) the charge on the capacitor
plates, (c) the electric field in the gap, and (d) the
electric field in the slab, after the slab is in place.
WOLFSON  CHAPTER 28
27. (b) in the 6.0 Ohm resistor? (c) in the 2.0 Ohm
resistor? (d) in the 1.0 Ohm resistor? (e) What is
the power output of the battery?