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 103. The exam period was 90 minutes; the mean score was 80.7 the median was 83. Click here to see 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}.

Which one of the following statements must be true?

(a) The magnitude of Q_{A} is less than the magnitude of q. (b) Q_{A} and q have the same sign. (c) Q_{B} and q have the same sign. (d) Q_{A} is positive and Q_{B}_{ }is negative. (e) Q_{A} is negative and Q_{B}_{ }is positive.

(a) always oriented parallel to the local gravitational field. (b) zero. (c) generally oriented perpendicular to any externally applied magnetic field

(a) 0.143 A (b) 0.200 A (c) 0.429 A

(a) 1.67 W (b) 5.00 W (c) 7.50 W

(a) 0.02 A (b) 0.08 A (c) 0.10 A (d) 0.71 A (e) 1.70 A

(a) E_{1} = 0.5 E_{2} (b) E_{1} = E_{2} (c) E_{1} = 2 E_{2}

Engineers at Nillog Lifts, Inc. design an elevator that uses a pair of positive charges Q = 0.1 C for propulsion. One is placed at the bottom of the elevator shaft, the other fixed to the bottom of the elevator car as shown in the diagram. Except for a braking system (not shown in the diagram), no other machinery is included in the elevator system.

Assuming that the fully loaded elevator car weighs 10,000 Newtons (roughly one ton), what is the maximum height to which the elevator can rise?

(a) 94.8 m (b) 900.0 m (c) 8.4 m

(a) The elevator can ascend but never descend. (b) The action of the electric charges might be cancelled by the Earth’s magnetic field, causing the elevator to fall uncontrollably.

Initially the capacitors C_{1} and C_{2} are uncharged and switch S is open. At time t = 0 the switch is closed and capacitors begin charging. At what time t does the voltage difference between points A and B reach 90% of the battery voltage E? (Recall that 1 ms is 0.001 seconds.)

(a) 3.06 ms (b) 7.68 ms (c) 15.4 ms (d) 17.2 ms (e) 37.6 ms

(a) 1.2 mA (b) 10 mA (c) 15 mA

(a) 0 V (b) 4 V (c) 8 V

(a) 12 μC (b) 10 μC (c) 8 μC

(a) 8.85 μF (b) 1 μF (c) 8.85 mF

(a) -6.75 × 10^{-3} N (b) -2.36 × 10^{-3} N (c) 0 N (d) +4.51 × 10^{-3} N (e) +9.44 × 10^{-3} N

(a) 7.02 × 10^{-3} J (b) 5.00 × 10^{-3} J (c) 8.41 × 10^{-3} J

(a) 0.068 J (b) 0.032 J (c) 0 J (d) -0.014 J (e) -0.021 J

(a) 25 Ω (b) 40 Ω (c) 55.5 Ω (d) 95.5 Ω (e) 300 Ω

The capacitors are initially uncharged. At time t = 0 the switch is closed. Which of the graphs below best represents the voltage difference between points A and B (V_{A}-V_{B}) as a function of time?

(a) graph a (b) graph b (c) graph c

(T) True (F) False

(a) 2.00 × 10^{-4} m (b) 1.78 × 10^{-3} m (c) 1.37 × 10^{-2} m (d) 4.63 × 10^{-2} m (e) 7.85 × 10^{-1} m

(a) 0.2 μF (b) 0.4 μF (c) 0.5 μF (d) 0.8 μF (e) 1 μF

(a) All electric field lines must leave one of the charges and arrive at the other charge. (b) The diagram indicates that the electric field becomes increasingly strong with increasing distance along the y axis, contrary to the behavior expected from Coulomb’s law. (c) Since field lines indicate the direction of force exerted on a positive charge, pairs of field lines must cross through each other along the y axis.

(a) 200 μC (b) 400 μC (c) 600 μC

In this circuit V = 12 V and C_{1} = C_{2} = 1 μF. How much energy is stored in capacitor C_{2}?

(a) 12 μJ (b) 36 μJ (c) 72 μJ

(a) It does not increase. (b) It increases by a factor of 1.732 . (c) It increases by a factor of 3 . (d) It increases by a factor of 9 . (e) It increases by a factor of 27 .

(a) minimized if the charge is moved along a single straight line from (2,2) to (1,1). (b) maximized if the charge is moved very far away, traveling parallel to the x axis, then moved directly to its final position at (1,1). (c) independent of the path taken to travel from (2,2) to (1,1).