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 122. The exam period was 90 minutes; the mean score was 84.4 the median was 85. 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}.

(a) 3.54 V (b) 12.5 V (c) 200 V

(a) (b) (c)

A lightning cloud-ground system can be modeled as a parallel plate capacitor. The cloud capacitor has capacitance = 2.27 × 10^{-6} F. The cloud is hovering at a height h = 1 km above the ground level. Think of the ground beneath the cloud as the other plate of the capacitor.

What is the area of a capacitor plate in this cloud-ground system?

(a) 2.56 × 10^{2} km^{2} (b) 5.20 × 10^{3} km^{2} (c) 3.91 × 10^{8} km^{2}

(a) 3.62 × 10^{-2} C (b) 1.32 × 10^{2} C (c) 2.27 × 10^{2} C (d) 5.79 × 10^{4} C (e) 3.62 × 10^{3} C

(a) attract each other electrically. (b) repel each other electrically. (c) atract or repel, depending on the sign of the charge.

A circuit has a 5 V battery, two resistors with values indicated below and a capacitor. There is a current I through the battery, I_{1} through the capacitor and I_{2} through resistor R_{1}.

What is the value of the current I_{1} right after the switch is closed? (There is no charge on the capacitor.)

(a) 0 A (b) 1.10 A (c) 1.67 A (d) 2.33 A (e) 9.31 A

(a) 0 A (b) 1.67 A (c) 2.5 A (d) 3.2 A (e) 4.17 A

(a) 0.10 A (b) 0.43 A (c) 0.50 A (d) 0.67 A (e) 1.33 A

A singly-ionized gold atom (mass = 3.27 × 10^{-25} kg, charge = +1.6 × 10^{-19} C) is placed precisely onto the center of a one- meter track. A uniform electric field of 5 × 10^{6}N/C is now turned on which points in the same direction as the track. The particle is accelerated to the end of the track where its velocity is measured. This velocity is discovered to be:

(a) 1.56 × 10^{6} m/s (b) 2.21 × 10^{6} m/s (c) 3.13 × 10^{6} m/s

(a) the speed of the particle when it exits the electric field (b) the direction the particle moves (c) the magnitude of the force on the particle

(a) 1.5 × 10^{5} m/s (b) 2.1 × 10^{5} m/s (c) 3.4 × 10^{5} m/s (d) 4.7 × 10^{5} m/s (e) 6.7 × 10^{5} m/s

(a) resistor A (b) resistor B (c) resistor C

Two charges are located as in the figure on the right and are equidistant from line B.

If two charges have the same amount of charge with the same sign, where is the electric field zero?

(a) at point A (b) on Line B (c) nowhere

(a) at point A (b) on Line B (c) infinitely far away

(a) pick up acceleration in the upward line B direction and escape. (b) begin a circular orbit. (c) will oscillate up and down along the line B direction at point A.

Object A hangs from an insulated thread. When object B, which has a charge of +130 nC, is held fixed nearby, A is attracted to it. In equilibrium, object A hangs at an angle θ = 7.20° with respect to the vertical and 5.00 cm left of B. The absolute value of the amount of charge for object A is 238 nC.

Would object A be positively or negatively charged?

(a) positive only (b) negative only (c) The sign doesn't matter.

(a) 882 g (b) 450 g (c) 90 g (d) 10 g (e) 1.47 g

(a) 921 pF (b) 438 nF (c) 1.32 μF (d) 2.50 μF (e) 5.03 μF

(x,y) : (-a,b), (-a,-b), (a,b), (a,-b), (0,c), (0,-c)

(a) north (b) south (c) east (d) west (e) It wouldn't move

(a) 0.0496 (b) 0.2444 (c) 0.4582 (d) 0.7847 (e) 1.000

(a) The energy increases. (b) The energy deceases. (c) The energy remains the same.

(a) 0.002 Ω*m (b) 0.019 Ω*m (c) 0.056 Ω*m (d) 0.075 Ω*m (e) 0.134 Ω*m

(a) -4.0 μJ (b) -2.0 μJ (c) 0 J (d) +2.0 μJ (e) +4.0 μJ

Consider the configuration of batteries and resistors depicted below. The batteries have potential differences of ε_{1} = 2 V, ε_{2} = 5 V, ε_{3} = 4 V. The resistors have resistances R_{1} = 10 Ω, R_{2} = 5 Ω, R_{3} = 20 Ω, R_{4} = 10 Ω.

What is the absolute value of the potential difference between points A and B?

(a) 0 V (b) 2 V (c) 4 V

(a) - ε_{1} + I_{2 }R_{2} - I_{3}R_{3}+ I_{1}R_{1} = 0 (b) - ε_{1} + ε_{2} + I_{1}R_{1} = 0 (c) + ε_{3} + I_{2 }R_{2} = 0

Below is an equipotential map generated by three charges (q_{1}, q_{2}, q_{3}). The value on each equipotential line is in volts. Note the signs (+/-).

Based on this map, answer these three questions.

What is the approximate direction of the electric field at point B?

(a) up (b) down (c) right (d) left (e) out of the page

(a) positive (b) negative

(a) W = -2 μJ (b) W = -1 μJ (c) W = 0 μJ (d) W = 1 μJ (e) W = 2 μJ