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 82.
The exam period was 60 minutes; the mean score was 45.8; the median was
46. Click here to see page1 page2 page3
of the formula sheet that came with the exam.
Some helpful information:
• A reminder about prefixes: p (pico) = 10-12; n (nano) =
10-9; μ (micro) = 10-6; m (milli) =
10-3; k (kilo) = 10+3; M or Meg (mega) =
10+6; G or Gig (giga) = 10+9.
This picture depicts an aluminum ring falling through a magnetic field
which points into the page and which gets gradually stronger at lower
In which direction does an induced current flow?
(b) counter clockwise
Suppose instead the ring were falling through a magnetic field that got
gradually weaker at lower heights. How would this experiment
differ from the previous question?
(a) The direction of magnetic force on the ring would reverse,
but not the direction of electric current.
(b) The current direction would reverse, but not the direction
of magnetic force.
(c) Both current and magnetic force would reverse direction.
Consider two parallel wires, one carrying current I1 = 5.8
A to the right, and at a distance L = 5 cm below it, another carrying
I2 = 2.6 A to the right.
What is the magnetic field a distance 10 cm above the top wire?
(a) 1.5 × 10-5 T, out of page
(b) 8.1 × 10-6 T, out of page
(c) 8.1 × 10-6 T, into page
(d) 1.16 × 10-5 T, into page
(e) 1.5 × 10-5 T, into page
(a) 1.04 × 10-5 N, upward along page
(b) 3.6 × 10-6 N, upward along page
(d) 3.6 × 10-6 N, downward along page
(e) 1.04 × 10-5 N, downward along page
(a) upward along page
(b) downward along page
(c) out of page
(d) into page
(e) it experiences no force
A proton (q = +1.6 × 10-19 C, m = 1.673 ×
10-27 kg) travels in a clockwise circle within a solenoid,
along the dashed line in the figure. The solenoid consists of 500 turns
of wire, and carries a current of 0.4 A, producing a magnetic field of
0.0022 T within the solenoid.
In which of these two directions could the magnetic field be
(a) into the page
(b) out of the page
(a) 11.4 cm
(b) 15.4 cm
(c) 19.4 cm
(a) the current flows clockwise
(b) the current flows counter-clockwise.
(a) 27 m/s
(b) 84 m/s
(c) 270 m/s
(d) 840 m/s
(e) 2700 m/s
The primary coil of a transformer, consisting of 180 turns of wire,
is connected to a voltage source of some kind. The secondary of that
transformer, consisting of 450 turns of wire, is connected to an
82 Ω resistor. The diagram might not accurately depict those
In which of these two situations is more energy dissipated, per second,
in the resistor?
(a) a 12 volt battery is connected to the primary
(b) a voltage source with Vrms = 6 volts is connected to the primary
(a) 0.54 A
(b) 0.76 A
(c) 1.35 A
(a) P2 = 0.16 P1
(b) P2 = 0.4 P1
(c) P2 = P1
(d) P2 = 2.5 P1
(e) P2 = 6.25 P1
A bar is free to slide along a pair of metal tracks separated by a
distance of L = 25 cm. (You may ignore friction between the bar and the
tracks.) At one end, the tracks are connected electrically by a
resistor R = 4.7 Ω. You should assume the metal bar completes an
electric circuit. You push the bar with a constant 0.18 N force, under
which the bar initially accelerates, but eventually reaches equilibrium,
ultimately moving at v = 4.6 meters per second. An unknown magnetic
field points into the page.
All the following questions assume the bar has reached equilibrium
and is therefore moving at a constant velocity.
What is the strength of the magnetic field?
(a) 1.7 T
(b) 2.9 T
(c) 4.4 T
(a) 0.18 W
(b) 0.23 W
(c) 0.27 W
(d) 0.34 W
(e) 0.83 W
In this RLC circuit, R = 270 Ω, L = 10 mH, and C = 0.7 μF.
A function generator, whose maximum voltage and operating frequency can
be adjusted, applies an alternating voltage.
Suppose the maximum current Imax = 12 mA when f = 410 Hz.
What average power is dissipated in the circuit?
(a) 0.019 W
(b) 0.026 W
(c) 0.039 W
(a) 0.43 V
(b) 6.37 V
(c) 9.90 V
(a) 1240 Hz
(b) 1900 Hz
(c) 12400 Hz
Fifteen turns of wire are wound in a circle of radius 3.5 cm. The
wire has a total resistance of 1.8 Ω. By connecting the loop to a
regulated motor, you can get it to spin at a constant angular frequency
ω =14 rad/sec in a magnetic field of strength B = 0.9 T. Define
θ to be the angle between the magnetic field and a vector
perpendicular to the plane of the loop. (In the picture, the loop
rotates around an axis perpendicular to the page.)
What current flows in the loop when θ = 0 ?
(b) 0.027 A
(c) 0.404 A
(a) 5 × 10-3 Nm
(b) 7 × 10-3 Nm
(c) 1.0 × 10-2 Nm
(d) 1.4 × 10-2 Nm
(e) 2.1 × 10-2 Nm