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 112. The exam period was 90 minutes; the mean score was 83.8; the median was 86. 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}.

A pair of conducting rails is connected to a resistor and a 5 V battery as shown in the following figure. A movable conducting bar is placed in contact with the rails. Initially the position of the conducting bar is held fixed. The entire device lies in a plane perpendicular to a magnetic field of strength 0.5 T.

The conducting bar is now moved slowly to the right. Relative to the current that had been flowing through the resistor while the bar was stationary, the current I

(a) increases. (b) decreases.

(a) 0.625 m/s (b) 2.5 m/s (c) 12.5 m/s (d) 40 m/s (e) 62.5 m/s

A conducting metal band containing a 5 Ω resistor is formed into a circle of radius R = 2 m as shown in the diagram. The band passes through a current sensor that also controls the strength of an adjustable, externally created magnetic field. (The electromagnet that creates this uniform field is not shown in the diagram.) The circle always lies in the plane of the paper, perpendicular to the magnetic field.

The current sensor/magnet power supply is programmed to adjust the external magnetic field so that a constant current of 0.1 A flows around the loop. At time t = 0 the magnetic field happens to have the value B = 0. What is the value of B at t = 1 second?

(a) B = 0.040 T (b) B = 0.100 T (c) B = 0.314 T (d) B = 1.687 T (e) B = 2.000 T

(a) ΔB/Δt would need to increase by a factor of 2. (b) ΔB/Δt would need to increase by a factor of 4. (c) ΔB/Δt would need to decrease by a factor of 2. (d) ΔB/Δt would need to decrease by a factor of 4. (e) ΔB/Δt would not need to change.

A rectangular loop (made from a single turn of wire) has sides a = 0.2 m and b = 0.1 m. The coil rotates about the y axis with angular velocity Ω = 20 rad/s in a uniform magnetic field B_{ }= 0.05 T that is parallel to the x axis. A light bulb with resistance 12 Ω is connected in series with the loop as shown in the diagram.

What is the maximum current that flows through the light bulb?

(a) 65.8 mA (b) 12.2 mA (c) 1.67 mA

(T) True (F) False

(a) 320 Hz (b) 2010 Hz (c) 50.9 Hz

The peak power delivered to the resistor attached to the transformer's secondary is 75 W. What is the signal generator's peak voltage?

(a) 1.5 V (b) 5.0 V (c) 20.4 V (d) 3750 V (e) 36000 V

What is the inductance of this solenoid?

(a) 0.612 H (b) 62000 H (c) 1.344 mH

In order to make the maximum value of V_{L} become less than the maximum value of V_{C} one could

(a) increase the maximum voltage of the sine wave generator. (b) decrease the frequency of the sine wave generator. (c) increase the value of R used in the circuit.

In the circuit shown the switch S is initially open and the two capacitors are fully discharged.

At time t = 0 the switch S is closed. What is the current through the resistor R immediately after S is closed?

(a) 10000 A (b) 2.5 mA (c) 0.0025 mA (d) 2.5 A (e) 10 mA

(a) I(25 msec) / I(0) = 0.361 (b) I(25 msec) / I(0) = 0.010 (c) I(25 msec) / I(0) = 0.650 (d) I(25 msec) / I(0) = 0.249 (e) I(25 msec) / I(0) = 0.189

In the circuit shown the switch S_{1} is initially open and the capacitor C is fully discharged.

Switch S_{1} is now closed. Which one of the following represents the correct time-dependence of the current through resistor R_{1}?

(a) (b) (c)

(a) 1.5 ms (b) 6 ms (c) 45 ms (d) 18 μs (e) 2.2 s

A charged particle, q, is moving in a uniform magnetic field and travels in a circle of radius R, as shown.

What is the sign of q?

(a) positive (b) negative

(a) 2.26 ×10^{-11} kg (b) 3.02 ×10^{-13} kg (c) 2.46 × 10^{-12} kg

A proton with charge q = +1.6 × 10^{-19} C and mass m = 1.67 × 10^{-27} kg is initially traveling horizontally in a magnetic field with velocity v = 800 m/s, as shown below. The proton experiences a downward acceleration due to gravity of g = 9.8 m/s^{2}. If the magnetic field were zero, the proton would follow the downward, parabolic trajectory shown in the dashed line.

How large a magnetic field would have to be applied to force the proton to move in a straight line?

(a) 5 × 10^{-8} T (b) 4.44 ×10^{-12} T (c) 1.5 T (d) 1.28 ×10^{-10} T (e) 23 mT

(a) (b)

How large would the current have to be to lift the cable off the ground? Recall, g = 9.8 m/s^{2}.

(a) 2.2 × 10^{6} A (b) 18600 A (c) 5325 A (d) 340 A (e) 52.9 A

In an RLC circuit, the following three elements are connected in series: a 10 mH inductor L, a 20 Ω resistor R, and a 120 μF capacitor C. The AC generator has a peak voltage of 1V, and a frequency of 50 Hz. Assume the resistance of the inductor is zero.

Across which of the following elements of the circuit is the maximum voltage drop the greatest?

(a) L (b) R (c) C

The following drawing indicates the voltage across the circuit elements as a function of time. The voltage drop across the resistor is labeled A (solid line). The voltage drops across which elements are shown by the dashed and dotted lines?

(a) C = generator; B = capacitor (b) C = inductor; B = capacitor (c) C = inductor; B = generator

(a) 1.29 A (b) 0.39 A (c) 32.5 mA (d) 92.8 mA (e) 0.21 mA

(a) 0° (b) 15.23° (c) -49.43° (d) -76.15° (e) 100. 3°

(a) The current leads the generator voltage. (b) The generator voltage leads the current.

(a) R (b) L (c) C

(a) 42.0 Hz (b) 145 Hz (c) 2.34 kHz

(a) increase. (b) decrease. (c) remain the same.