True-false questions are worth 2 points each,
three-choice multiple choice questions are worth 3 points each,
five-choice multiple choice questions are worth 6 points each. The
maximum possible score is 108. The exam period was 90 minutes; the mean
score was 79.5; the median was 81. Click here to see
page2 of the formula sheet that came
with the exam.
A solid, infinite metal cylinder of radius a = 1.5 cm is
centered on the origin, and has charge density
λinner = -5 nC/cm. Surrounding this cylinder
is a cylindrical metal shell of inner radius b = 3.0 cm and outer
radius c = 4.5 cm. This shell is also centered on the origin,
and has total charge density λshell = +2 nC/cm.
If a positive point charge were placed on the x-axis at
the location x = 8 cm and released from rest, it would
(a) move away from the origin.
(b) move toward the origin.
(c) remain at rest.
(a) |E| = 1.8×104 N/C
(b) |E| = 3.2×104 N/C
(c) |E| = 4.6×104 N/C
(d) |E| = 6.7×104 N/C
(e) |E| = 1.3×105 N/C
(a) Va - Vc = -8.7 kV
(b) Va - Vc = -6.2 kV
(c) Va - Vc = 0
(d) Va - Vc = +6.2 kV
(e) Va - Vc = +8.7 kV
(a) λsh,outer = +3 nC/cm
(b) λsh,outer = 0 nC/cm
(c) λsh,outer = -3 nC/cm
(a) σinner = 0
(b) σinner = -0.53 nC/cm2
(c) σinner = -3.33 nC/cm2
(a) increase in magnitude.
(b) be zero.
(c) remain unchanged.
A solid spherical insulator has radius R = 2.5 cm,
and carries a total positive charge Q = 8 ×
10-10 C distributed uniformly throughout its volume.
Find the magnitude of the electric field |E| at a
radius of 5 cm from the origin (i.e., outside the sphere).
(a) |E| = 2.88×103 N/C
(b) |E| = 8.92×103 N/C
(c) |E| = 2.41×104 N/C
(d) |E| = 5.01×104 N/C
(e) |E| = 8.30×104 N/C
(a) V = +2500 V
(b) V = +985 V
(c) V = -144 V
(d) V = -2500 V
(e) V = -3700 V
The electric field lines (solid) and the equipotential lines (dashed) in a
certain region of space are as shown here.
When a positive charge is moved from point A to point D, the work
done by the electric field is
(a) greater than the work done by the field when the same charge
is moved from point B to point C.
(b) equal to the work done by the field when the same charge is moved from
point B to point C.
(c) less than the work work done by the field when the same charge is moved
from point B to point C.
(a) greater than the electric potential at B.
(b) equal to the electric potential at B.
(c) less than the electric potential at B.
Two charged, thin, metal plates of infinite area are placed in the
planes x = -a and x = +a, as shown in the
figure. Each plate carries a negative surface charge density
σp = -3 μC/m2. Finally, a metal
slab of thickness a and infinite area is placed so that its
left-hand surface coincides with the plane x = +3a. This
metal slab carries a total positive charge density
σs = +8 μC/m2.
The potential energy of a positive charge moving from point B
to point A will
(b) remain constant.
(a) |E| = |σp| / ε0
(b) |E| = |σs| / ε0
(c) |E| = |σs| / (2ε0)
(d) |E| = |σs+2σp| / (2ε0)
(e) |E| = |σs-2σp| / (2ε0)
(a) σR = σs / 2
(b) σR = 2σp
(c) σR = (σs + σp) / 2
(d) σR = (σs/2) + σp
(e) σR = 0
(a) be repelled by a charged metal surface.
(b) feel no force when brought close to a charged metal surface.
(c) be attracted by a charged metal surface.
A positive point charge q = +3 μC is placed on the y
axis at y = +5 cm. A negative point charge -q = -3 μC
is placed at the origin.
At how many points on the y axis could an additional positive
charge +q be placed without changing the potential energy of the
(a) no points
(b) 1 point
(c) 2 points
(a) W = 2.98 J
(b) W = 0.47 J
(c) W = 0 J
(d) W = -1.36 J
(e) W = -5.19 J
(a) U > 0
(b) U = 0
(c) U < 0
The circuit at left contains 3 capacitors, all of initial value C
= 3 μF.
What is the charge Q1 on capacitor C1?
(a) Q1 = 18.3 μC
(b) Q1 = 21.4 μC
(c) Q1 = 27 μC
(d) Q1 = 30.8 μC
(e) Q1 = 33.7 μC
(a) Q2 = 9.1 μC
(b) Q2 = 13.5 μC
(c) Q2 = 21.4 μC
(d) Q2 = 33.7 μC
(e) Q2 = 42.8 μC
(a) Q2 decreases because the capacitance of
C2 decreases relative to that of C3.
(b) Q2 stays the same because the charge of capacitors in
series is the same.
(c) Q2 increases because the capacitance of C3
(a) Q1 decreases because the capacitance of
C1 decreases relative to that of C3.
(b) Q1 stays the same because the voltage across
C1 is the same as it was originally.
(c) Q1 increases because the effective capacitance of the
C2 C3 part of the circuit increases.
The X-ray tube shown at right is used to accelerate electrons which
hit a target and produce X-rays. The device consists of two parallel,
metal plates of very large area separated by a 10 cm gap. The plate on
the left ("cathode") is connected to ground, while the plate on the
right ("anode") is set to a potential of +11 kV. Electrons are
produced (at rest) at the cathode plate. They accelerate across the
gap, and strike the target area where they slow down rapidly and produce
Calculate the final speed v achieved by electrons of mass
m = 9.1 × 10-31 kg and charge magnitude
|q| = 1.6 × 10-19 C.
(a) v = 9.1 × 105 m/s
(b) v = 7.3 × 106 m/s
(c) v = 2.3 × 107 m/s
(d) v = 6.2 × 107 m/s
(e) v = 4.1 × 108 m/s
(a) σ = 0.49 μC/m2
(b) σ = 0.97 mC/m2
(c) σ = 1.24 μC/m2
(d) σ = 1.56 μC/m2
(e) σ = 1.95 μC/m2
(a) to the right on the right side of the tube and to the left
on the left side of the tube.
(b) to the left on the right side of the tube and to the right on the left
side of the tube.
(c) the field will be zero everywhere to the left of the cathode and to the
right of the anode.