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 94. The exam period was 75 minutes; the mean score was 63.3 the median was 66. Click here to see page1 page2 page3 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}.

In lecture a van de Graaff generator was used to build up a large charge. Nearby, there was a grounded metal sphere; and between the grounded metal sphere and the generator, an (initially) uncharged metal sphere hung from a string, allowed to swing back and forth between the generator and the grounded sphere.

What can we say about that hanging metal sphere?

(a) Because it was initially uncharged, it would initially experience no net force from the van de Graaff generator. (b) A charged van de Graaff generator will attract the hanging metal sphere, regardless of the sign of the charge on the van de Graaff generator. (c) The negatively-charged van de Graaff generator attracted the neutral hanging sphere but a positively-charged generator would repel the neutral hanging sphere.

(T) True (F) False

(a) The capacitance increases and the voltage decreases. (b) The capacitance and the charge both decrease. (c) The voltage increases but the charge remains the same.

A pair of charges sits on the x-axis, a charge Q_{1} = +9 nC at the origin and Q_{2} = +4 nC at x = 5. Assume no other charges are present. All coordinates are in meters.

At which one of these points is the net electric field equal to zero?

(a) x = 15 (b) x = 9 (c) x = 4 (d) x = 3 (e) x = 2

(a) -12.6 V (b) +12.6 V (c) +19.8 V

(a) -43.2 nJ (b) -23 nJ (c) 23 nJ (d) 43.2 nJ (e) 108 nJ

A negative charge Q_{1} = -8 nC is fixed on the x-axis at (x = -4, y = 0). A positive charge Q_{2} = +8 nC is fixed on the x-axis at (x = 4, y = 0). For the sake of reference, consider point A, at (x = 0, y = 5). All locations are in meters.

What is the sign of the x-component of the electric field at A?

(a) negative (b) zero (c) positive

(a) 0 N/C (b) 1.76 N/C (c) 2.19 N/C (d) 2.74 N/C (e) 3.51 N/C

(a) 72 nJ (b) 9 nJ (c) 0 (d) -9 nJ (e) -72 nJ

(a) 9 W (b) 27 W (c) 54 W (d) 84.6 W (e) 108 W

Consider this circuit.

What is the voltage across the 6 μF capacitor?

(a) 10 V (b) 12 V (c) 18 V (d) 20 V (e) 30 V

(a) 2700 μJ (b) 4050 μJ (c) 5850 μJ (d) 12150 μJ (e) 24300 μJ

(a) 2.0 (b) 2.25 (c) 2.5

Five resistors are connected as shown.

Find the single resistance equivalent to this network.

(a) 21.3 Ω (b) 25.6 Ω (c) 32 Ω (d) 34 Ω (e) 88 Ω

(a) The voltage is greater without that resistor. (b) The voltage will be unaffected by the removal of that resistor. (c) The voltage is smaller without that resistor.

(a) Yes, it has the same resistance (b) No, it is different

Which one of the following equations is true?

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

6 I_{1} - 8 I_{2} - 4 = 0

is valid for this circuit.

-9 + 6 I_{1} – 22 I_{3} – 14 = 0

The capacitor in this circuit is initially uncharged. At time t = 0, switch S_{1} is closed but switch S_{2} is left open. After a very long time has elapsed, a charge Q = 3.0 μC will be stored on the capacitor. What must the charge Q on the capacitor have been after a time equal to 2 time constants (t = 2τ) had elapsed?

(a) 0.4 μC (b) 2.6 μC (c) 3.0 μC

(a) 5.7 mA (b) 8.5 mA (c) 14.2 mA

(a) 0.35 ms (b) 0.53 ms (c) 0.88 ms

(a) 1.2 μC (b) 1.8 μC (c) 3.0 μC: