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 100. The exam period was 90 minutess; the mean score was 66.4; the median was 67. 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}.

What is the maximum voltage produced across the resistor by the coil?

(a) 20 mV (b) 50 mV (c) 240 mV

V(t) = 480 sin(ωt)

(a) 480 V (b) 339.4 V (c) 240 V

A solenoid of length 0.5 m and radius .03 m is wound with 1000 turns.

What is the inductance of this solenoid?

(a) 7.1 mH (b) 3.55 mH (c) 14.2 μH

(a) 1.88 mT (b) 2.5 mT (c) 3.77 mT

(a) decreased. (b) increased. (c) not changed.

The phasor diagram at the left corresponds to a series RCL circuit driven by a sine wave generator with maximum voltage of 30 V. The magnitudes of R, X_{L} and X_{C} are labeled on the phasor diagram.

What is the magnitude of the total impedance Z of the circuit?

(a) 190 Ω (b) 50 Ω (c) 70 Ω

(a) 18 V (b) 30 V (c) 15 V (d) 25 V (e) 10 V

The phase angle Φ describes the phase relationship between the voltage supplied by the signal generator, V(t) = V_{max}sin(2πft + Φ), and the current that flows in the circuit, I(t) = I_{max}sin(2πft). What is the phase angle at frequency f = 600 Hz ?

(a) 56.9° (= 0.993 radians) (b) -56.9° (= -0.993 radians) (c) 27° (= 0.471 radians) (d) -27° (= -0.471 radians) (e) 35.5° (= 0.620 radians)

(a) 600 W (b) 543.8 W (c) 300 W

A conducting metal band containing a 5 Ω resistor is formed into a circle of radius R as shown in the diagram. The band runs through a computer-controlled motorized screw-drive so that the circumference of the band changes as the screw-drive turns, changing the size of the circle smoothly as dictated by the computer. The circle always lies in the plane of the paper, perpendicular to a uniform magnetic field B of 0.25 T.

The computer-controlled screw drive turns so as to decrease the circumference of the loop. Because of this,

(a) a current that flows clockwise is induced in the loop. (b) a current that flows counterclockwise is induced in the loop.

(a) 50 mA (b) 35 mA (c) 10 mA (d) 5 mA (e) 1 mA

The magnitude of the current induced in the loop is greatest at which of the following times?

(a) t = 0.5 (b) t = 1.0 (c) t = 1.5

A transformer with a 100-turn primary coil and 300-turn secondary coil is wired to a signal generator and 50 Ω resistor as shown in the following diagram. The signal generator produces a 60 Hz sine wave.

The signal generator's peak voltage is 24 volts. How much peak power is delivered to the resistor attached to the transformer's secondary?

(a) 11.52 W (b) 72 W (c) 103.68 W (d) 1200 W (e) 15000 W

(a) P_{signal generator} / P_{resistor} = 0.25 (b) P_{signal generator} / P_{resistor} = 1 (c) P_{signal generator} / P_{resistor} = 4

A generator is built by winding 30 turns around a circular form of radius 0.1 m and then attaching it to a horizontal motor-driven shaft as shown in the figure below. The loop rotates in a uniform vertical magnetic field of strength B = 0.3 T; the wire of the loop is somewhat resistive so that the total resistance of the 30 loops is 4 Ω. The angle Φ between the normal to the loop and the magnetic field obeys the equation Φ = 75t radians. (This means that ω = 2πf = 75 radians/second.)

At the time t shown in the diagram, Φ = π/2 radians = 90°.

When the orientation of the loop is as shown in the figure, the flux of magnetic field through the loop is at its maximum value.

(T) True (F) False

An American traveller with an electric razor enters a hardware store in Toledo hoping to buy a transformer to convert 110 V, 50 Hz power into U.S. standard 110 V, 60 Hz power. He describes his problem to the proprietor and asks for help. The owner of the hardware store explains that he should buy

(a) a transformer whose primary has 1.2 times as many windings as its secondary. (b) a transformer whose secondary has 1.2 times as many windings as its primary. (c) razor blades and shaving cream since transformers convert voltage, but not frequency

You are trying to make isotopically pure Uranium^{235} to sell on the black market. You have a mixture of U^{235} and U^{238} which you are trying to separate by ionizing it and passing it through a region with uniform 1.5 T magnetic field, after which the ions strike a screen. The masses of the two isotopes are M_{238} = 3.95 × 10^{-25} kg and M_{235} = 3.90 × 10^{-25} kg. The ions are all singly ionized so they have charge q_{235} = q_{238} = +1.6 × 10^{-19} C. All ions have the same velocity, as shown, of v = 100 m/s. The magnetic field is into the page.

Which of the two isotopes strikes higher on the screen?

(a) U^{235} (b) U^{238}

(a) 60.25 T (b) 6.25 T (c) 0.625 T (d) 0.0625 T (e) 0.00625 T

(a) π / 2 (b) 2 π (c) 1 / 2

A particle of charge q = -3 μC is traveling with speed v = 50 m/s in a uniform field B = 4 T, as shown. θ = 22.5°.

What is the force on the particle?

(a) 55.4 μN out of the page (b) 230 μN into the page (c) 230 μN out of the page (d) 554 μN into the page (e) 23.0 μN into the page

(a) a helix. (b) a circle oriented in the plane of the page. (c) a circle oriented perpendicular to the page.

A square, horizontal loop with side length L = 0.1 m is attached to a pivot around which it may freely rotate. A magnetic field B = 0.5 T is applied parallel to the plane of the loop, as shown. A battery (not shown) forces a constant current to flow around the loop.

Because of the torque exerted by the magnetic field, the loop would begin to rotate were it not for a mass m = 1 kg suspended from one side of the loop. Recall that g = 9.8 m/s^{2}.

Which way must the current flow in the loop to keep it from rotating due to the weight of the mass?

(a) as indicated by the arrow marked "A" (b) as indicated by the arrow marked "B"

(a) 196 A (b) 98 A (c) 49 A (d) 24.5 A (e) 12.25 A

A two-loop circuit is attached to a rotating pivot and suspended in a uniform magnetic field, B, pointing to the right. R = 1 Ω, V = 10 V, B = 1 T , and L = 1 m.

Initially the switch S is closed. In which direction will the loop turn? (Refer to the arrows drawn around the pivot.)

(a) as indicated by arrow A (b) as indicated by arrow B (c) The loop will not turn.

(a) 0.1 N-m (b) 0.5 N-m (c) 1 N-m (d) 5 N-m (e) 10 N-m