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 81.
The exam period was 75 minutes; the mean score was 49.2; the median was
here to see page1
page3 of the formula sheet that came
with the exam.
As in lecture, a cylindrical magnet ('cow magnet') is released to
fall through a narrow copper pipe. Assume, as shown, that it is dropped
with the north pole closer to the ground. The tube is at rest; arrow is
drawn only for the sake of reference.
An induced current flows in the direction indicated by the arrow
(which shows a current flowing left to right in the part of the copper
pipe closest to you).
(a) There will be no emf in the PVC pipe.
(b) There will be an emf in the PVC pipe.
(a) The induced current and the force on the cow magnet will be the same in both
(b) The induced current will reverse direction but the force will be the same in
(c) Both induced current and force on the magnet will switch directions when the
poles are reversed.
A charge (|q| = 1.6 × 10-19C, m = 1.673
× 10-27 kg) enters a circular region in which a
constant field (B = 0.08 T) points out of the page. It enters
moving vertically at the exact bottom of the field and emerges
moving horizontally at the rightmost side. Ignore all forces
other than that exerted by the magnetic field. Call the radius of this
circular region r.
What is the sign of the charge?
(a) 1200 m/s
(b) 1700 m/s
(c) 2 × 105 m/s
(d) 1 × 106 m/s
(e) 8 × 106 m/s
(a) 8 × 10-7 sec
(b) 5 × 10-6 sec
(c) 7 × 10-6 sec
A square loop of side 1 cm moves at constant velocity to the right of 1
cm/sec. It moves from a field-free region on the left into a uniform
magnetic field and then back into the field-free region on the right.
The field points into the page. The region in which the field is
contained is 5 cm wide. The loop has a total resistance of 500 Ω.
At various times a current may be detected in the square loop. For
how many seconds, in total, will this current flow?
(a) 1 sec
(b) 2 sec
(c) 3 sec
(d) 5 sec
(e) 6 sec
(a) I = 1 × 10-3 A
(b) I = 1 × 10-5 A
(c) I = 1 × 10-7 A
(a) The top segment is pulled to the left.
(b) The top segment is pulled upward along the page.
(c) The top segment is pulled downward along the page.
Consider the AC circuit shown here. The resistor R = 1000
Ω, the capacitive reactance XC = 1800 Ω,
and the inductive reactance XL = 900 Ω. The
function generator produces a voltage given by the formula
Vgen(t) = 40 sin(800t).
Calculate the capacitance.
(a) 0.7 μF
(b) 2.2 μF
(c) 4.4 μF
(a) 19 V
(b) 27 V
(c) 34 V
(d) 37 V
(e) 40 V
(a) 0.31 W
(b) 0.44 W
(c) 0.63 W
(d) 0.88 W
(e) 0.99 W
(a) It increases.
(b) It decreases.
The diagram shows a wire loop of height 8 cm and width 4 cm. The loop
has a total resistance R = 15 Ω. A magnetic field of
strength B = 0.9 T points into the page. In the first question,
a battery is connected, causing a current to flow. Points P and
Q are labeled for the sake of reference.
If an 18 volt battery is attached, what is the magnitude of the
torque acting on this loop?
(b) 0.0035 Nm
(c) 35 Nm
In which direction does the induced current flow?
(a) from P towards Q
(b) from Q towards P
(a) 1.0 rad/sec
(b) 0.63 rad/sec
(c) 0.38 rad/sec
(a) 0.6 × 10-7 Nm
(b) 1.3 × 10-7 Nm
(c) 2.1 × 10-7 Nm
(d) 3.5 × 10-7 Nm
(e) 4.5 × 10-7 Nm
This diagram shows a pair of very long wires carrying currents
I1 = 0.4 A and I2 = 1.6 A, both
flowing to the right. The wires are separated by L = 15 cm.
Which one of these is true?
(a) These two wires repel each other.
(b) These two wires attract each other.
(a) nowhere between them
(b) 10 cm above the bottom wire
(c) 12 cm above the bottom wire
(a) 3.4 × 10-8 N
(b) 5.1 × 10-8 N
(c) 8.5 × 10-8 N
(d) 1.7 × 10-7 N
(e) 2.1 × 10-7 N
(a) 9 V
(b) 11 V
(c) 12 V
(a) 6 W
(b) 8.5 W
(c) 12 W
(d) 17 W
(e) 24 W