This exam consists of 31 questions; 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 143. When the exam was given, the mean was 96.8; the median was 98. Click here to see the formula sheet that came with the exam.

(a) left (b) right (c) up (d) down (e) the force is zero

(a) (b) (c) (d) (e)

Four charges are fixed at the corners of a square of sides 4m as shown.

What is the electric potential at the center of the square?

(a) -92.6 N-m/C (b) -38.2 N-m/C (c) 0 N-m/C (d) +38.2 N-m/C (e) +92.6 N-m/C

(a) 13.9 N/C (b) 27.0 N/C (c) 37.3 N/C (d) 55.1 N/C (e) 84.0 N/C

(a) along the vertical (b) along the horizontal (c) along the diagonal

(a) 1.68 × 10^{-8} N (b) 2.37 × 10^{-8} N (c) 4.74 × 10^{-8} N (d) 7.70 × 10^{-8} N (e) 9.78 × 10^{-8} N

Two small spheres with equal unknown mass are suspended by light-weight strings of length 10 cm. When a charge of +5 nC is placed on each sphere, each string makes an angle of 20° with the vertical in equilibrium.

What is the mass of each ball?

(a) 1.21 × 10^{-6 }kg (b) 3.56 × 10^{-6 }kg (c) 1.07 × 10^{-5 }kg (d) 1.35 × 10^{-5 }kg (e) 2.23 × 10^{-5 }kg

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

A small particle with charge +15e (e = 1.6 x 10^{-19} C) is located at the origin, a distance of 5 nm from a second particle of charge –30e.

What is the potential energy of the two-charge system?

(a) -6.90 × 10^{-9} J (b) -8.98 × 10^{-12} J (c) -3.33 × 10^{-15} J (d) -2.07 × 10^{-17} J (e) -4.15 × 10^{-19} J

(a) 2.50 nm (b) 2.89 nm (c) 3.71 nm (d) 7.35 nm (e) 10.00 nm

How much work is required to move this particle to the position +10 nm on the x-axis?

(a) 0 J (b) 6.65 × 10^{-19} J (c) 9.56 × 10^{-19} J (d) 1.24 × 10^{-18} J (e) 5.18 × 10^{-18} J

Four capacitors are connected as shown. A 15 V battery is centered in the circuit. Assume that all of the capacitors are fully charged and that no current is flowing.

What is the charge on one of the plates of the 4mF capacitor?

(a) Q_{4} = 15 mC (b) Q_{4} = 30 mC (c) Q_{4} = 60 mC

(a) U_{tot} = 0.054 × 10^{-3} J (b) U_{tot} = 0.420 × 10^{-3} J (c) U_{tot} = 0.875 × 10^{-3} J (d) U_{tot} = 1.125 × 10^{-3} J (e) U_{tot} = 2.660 × 10^{-3} J

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

(a) C_{eq} = C_{0} / 4 (b) C_{eq} = C_{0} / 2 (c) C_{eq} = C_{0} (d) C_{eq} = 2C_{0} (e) C_{eq} = 5C_{0}

An isolated parallel-plate capacitor has area A = 3.0 ´ 10^{-4} m^{2} and plate separation d = 2 ´ 10^{-5} m. The charge on each plate has magnitude Q = 11 nC. The capacitor is initially filled with air (k = 1).

Compute the energy stored in the capacitor.

(a) U = 2.31 × 10^{-8 }J (b) U = 4.32 × 10^{-8 }J (c) U = 9.06 × 10^{-8 }J (d) U = 1.51 × 10^{-7 }J (e) U = 4.56 × 10^{-7 }J

A single charge of unknown sign and magnitude is located at the origin. A graph of the electrical potential a distance r away from this charge is shown below. We assume that the potential at infinity is zero. The graph is accurately prepared so you can read meaningful values from scales on the axes.

The sign of the charge is

(a) positive. (b) negative.

(a) | Q | = 0.22 nC (b) | Q | = 5.55 nC (c) | Q | = 50.0 nC

(a) W = 0.15 µJ (b) W = 0.80 µJ (c) W = 1.33 µJ (d) W = 8.66 µJ (e) W = 25.0 µJ

Which one of the following is a valid Kirchhoff voltage equation for the dotted outside loop?

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

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

Compare I_{2}, the current through R_{2}, with I_{3}, the current through R_{3}.

(a) I_{2} > I_{3} (b) I_{2} = I_{3} (c) I_{2} < I_{3}

(a) V_{3} > V_{4} (b) V_{3} = V_{4} (c) V_{3} < V_{4}

(a) P = 1.95 W (b) P = 5.32 W (c) P = 11.9 W (d) P = 25.8 W (e) P = 28.8 W

(a) I_{2} = 0.248 A (b) I_{2} = 0.387 A (c) I_{2} = 0.459 A (d) I_{2} = 0.521 A (e) I_{2} = 0.692 A

In this circuit, the switch has been open for a long time so that the capacitor is uncharged.

What is the current through the battery immediately after the switch is closed?

(a) I(0+) = 0 (b) I(0+) = V / R (c) I(0+) = 2 V / R

(a) I(¥) = 0 (b) I(¥) = V / R (c) I(¥) = 2 V / R

(a) Q(¥) = C V / 2 (b) Q(¥) = C V (c) Q(¥) = 2 C V

(a) t = 13.8 µs (b) t = 41.3 µs (c) t = 55.5 µs (d) t = 88.1 µs (e) t = 113.2 µs