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 109.
The exam period was 90 minutes; the mean score was 73.6; the median was
75. Click here to see page1
page2 of the formula sheet that came
with the exam.
Some helpful information:
• A physics 102 light bulb acts just like a resistor: its resistance
is constant, independent of the current flowing through the light bulb.
The bulb's brightness increases with increasing current.
• 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.
Two currents are flowing in the same direction (out of the page) as
What is the magnitude of magnetic field at wire #1 due to the current
in wire #2?
(a) 8 × 10-8 T
(b) 4 × 10-8 T
(c) 2.5 × 10-7 T
(c) out of the page
(a) It will double.
(b) It will increase by a factor of four.
A charged particle of mass m = 0.001 kg enters a region of constant
magnetic field (10 T, out of the page) and exits after following a
trajectory as shown. Its location in the horizontal direction is
displaced by d = 0.2 meter when it exits compared to its location upon
entry. The speed of the particle before it entered the region of
constant magnetic field is 100 m/s.
What is the value of the charge?
(a) +0.1 C
(b) +0.02 C
(c) -0.003 C
(d) -0.02 C
(e) -0.1 C
(a) 100 m/s
(b) 200 m/s
(c) 50 m/s
A square loop (L = 0.1 m for each side) is placed in a region of
constant magnetic field (B = 0.1 T, to the right). The
plane of the loop makes an angle of 30° with respect to
horizontal as shown. A current (I = 0.1 A) is flowing in the loop in
the direction illustrated.
What is the magnitude of torque applied to this loop?
(a) 8.7 × 10-5 N-m
(b) 5.0 × 10-5 N-m
(c) 2.9 × 10-5 N-m
What is the magnitude of the magnetic force on the electron?
(a) 2.3 × 10-22 N
(b) 3.2 × 10-22 N
(c) 5.1 × 10-22 N
(d) 6.5 × 10-22 N
(e) 8.4 × 10-22 N
An "American Idol" contestant ends her performance by singing a
perfect C# into a microphone. Her microphone works as shown in the
figure below: a magnet attached to a diaphragm moves back and forth
in response to the sound waves, moving in and out of a coil.
The magnet oscillates back and forth in response to her voice such
that the magnetic flux though the coil changes in time as shown
in the plot at right.
Which one of the following graphs most accurately describes the
emf in the coil?
(a) It would double.
(b) It would remain the same.
(c) It would be halved.
Two ideal transformers are connected as shown below. The
first transformer (on the left) has 5 turns on the primary and 10
turns on the secondary, and the second transformer (on the right)
also has 5 turns on the primary and 10 turns on the secondary. A
100 Ω resistor is placed across the secondary of the second
transformer. A voltage source supplies a 60 Hz sinusoidal voltage with a
maximum of 10 V. Note that the voltage at the secondary of the first
transformer is the same as the voltage at the primary of the second
Calculate the maximum voltage across points a and b on
(a) 5 V
(b) 10 V
(c) 20 V
(a) 0.1 A
(b) 0.2 A
(c) 0.4 A
(d) 0.8 A
(e) 1.6 A
(a) Psource > Presistor
(b) Psource = Presistor
(c) Psource < Presistor
A generator consists of a coil with 10 turns and an area of
0.01 m2 spinning in a uniform magnetic field of magnitude
0.1 T. The generator drives a light bulb with a resistance of 200
The current in the light bulb cannot exceed 0.5 A; otherwise it burns
out. What is the maximum rate at which the coil can spin so that
the current does not exceed this limit?
(a) 1 × 104 revolutions/second
(b) 1 × 105 revolutions/second
(c) 1.6 × 103 revolutions/second
(d) 1.6 × 104 revolutions/second
(e) 3.2 × 104 revolutions/second
A solenoid is connected to a battery with a switch. The ends of a
second solenoid are connected to an ammeter.
The switch in the first solenoid is closed. In what direction does
the current flow in the ammeter connected to the second solenoid
immediately after the switch is closed?
(a) to the right
(b) to the left
(a) the same as in the previous question
A machine that manufactures inductors is adjusted to make cylindrical
coils of diameter 5 mm and length 20 mm. Each inductor is wound with
300 turns of wire.
What is the inductance of an inductor built with these
(a) 0.016 μH
(b) 111.0 μH
(c) 325.0 μH
(a) L300 / L600 = 0.25
(b) L300 / L600 = 0.50
(c) L300 / L600 = 1.00
(d) L300 / L600 = 2.00
(e) L300 / L600 = 4.00
Which one of the following graphs best represents the
energy U(t) stored in the inductor?
The generator is programmed to keep the amplitude of
the current constant, but to double the
frequency at a preset time. An oscilloscope is used to
observe the voltage across the mystery circuit element.
The current I(t) provided by the AC generator, before
and after the frequency is doubled (but the amplitude is held constant),
is shown in the following graphs.
The voltage V(t) across the mystery object (as shown by
the oscilloscope) is indicated in the following diagrams. Note that the
voltage amplitude doubles.
The mystery object hidden inside the box is probably
(a) a resistor.
(b) an inductor.
(c) a capacitor.
The second oscilloscope trace labeled Vx -
(a) the voltage drop across the capacitor: VC =
V2 - V3.
(b) the voltage drop across the inductor: VL =
V3 - V4.
(c) the power dissipated by the capacitor.
(d) the total reactance (impedance) of the circuit.
(e) the energy stored in the inductor.
An AC generator in the LRC circuit shown in the following
figure produces a voltage V(t) =
values of inductance, capacitance, and resistance are shown on the
diagram. Recall that ω = 2πf.
The rms voltage supplied by the AC generator is
(a) 0.50 V
(b) 0.707 V
(c) 1.00 V
(a) 141 mA
(b) 12 mA
(c) 2.71 mA
(d) 377 mA
(e) 105 mA
An LRC circuit and a voltage phasor diagram for this circuit
are shown in the following figure. The period T =
2π/ω of the voltage produced by the AC generator is 10
At the instant in time represented by the phasor, across which
circuit element is the largest voltage difference to be found?