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 124. The exam period was 90 minutes; the mean score was 86.3 the median was 88. 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) right (b) left (c) down

What is the ratio of the resistances R_{1} / R_{2} ?

(a) 4/9 (b) 2/3 (c) 1 (d) 3/2 (e) 9/4

Two spheres of equal mass are suspended by light-weight strings of length 15 cm each. When a charge of -4 nC is put on each sphere, each string makes an angle of 30° with the vertical in equilibrium.

What is the mass of each sphere?

(a) 3.39 × 10^{-}^{7} kg (b) 1.69 × 10^{-}^{7} kg (c) 1.13 × 10^{-}^{6} kg (d) 2.82 × 10^{2} kg (e) 1.13 × 10^{3} kg

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

Four capacitors are connected as shown below. A 12 V battery is centered in the circuit. Assume that every capacitor is fully charged and no current is flowing.

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

(a) Q_{4} = 0.33μC (b) Q_{4} = 3μC (c) Q_{4} = 48μC

(a) U_{tot} = 7.80 × 10^{-}^{5} J (b) U_{tot} = 1.56 × 10^{-}^{4} J (c) U_{tot} = 9.36 × 10^{-}^{4} J (d) U_{tot} = 1.87 × 10^{-}^{3} J (e) U_{tot} = 3.74 × 10^{-}^{3} J

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

A simple circuit consists of a battery (ε = 10 V), a resistor (R = 12 Ω), and a capacitor (C = 0.2 μF) in series. If the capacitor is uncharged at t = 0, how long will it take for the potential difference across the capacitor to reach 6 V?

(a) 0.8 μs (b) 1.2 μs (c) 2.2 μs (d) 3.5 μs (e) 4.6 μs

(a) (b) (c)

(a) When the bulbs are connected in parallel they will be the brightest. (b) When the bulbs are connected in series they will be the brightest. (c) The brightness will be the same regardless of whether they are in series or parallel.

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

What is the work done by you to assemble the charges?

(a) -5.91 × 10^{-2} J (b) -2.39 × 10^{-2} J (c) -0.239 × 10^{-2} J (d) 2.39 × 10^{-2} J (e) 5.91 × 10^{-2} J

(a) -3110 N/C (b) 2540 N/C (c) 3310 N/C (d) 4880 N/C (e) 7080 N/C

What is the value of I_{3}?

(a) .17 A (b) .33 A (c) .5 A (d) .83 A (e) 1 A

(a) .3 A (b) .97 A (c) 1.33 A (d) 2.57 A (e) 3 A

(a) decrease by a factor of four. (b) decrease by a factor of two. (c) remain unchanged. (d) increase by a factor of two. (e) increase by a factor of four.

(a) R' = 0.173R (b) R' = 0.417R (c) R' = 2.4R (d) R' = R (e) R' = 5.76R

(a) north (b) south (c) east (d) west (e) out of the page

(a) 0.067 Ω (b) 0.438 Ω (c) 2.28 Ω (d) 4.67 Ω (e) 15 Ω

A neuron can be modeled as a parallel plate capacitor, with the membrane acting as a dielectric and ions as charges on the plates. The membrane has a dielectric constant κ = 7.0 and a thickness of d = 6 nm.

In its resting state, the inside of the cell is at a potential of -85 mV relative to the outside.

What is the capacitance of a 1 (μm)^{2} (10^{-12} m^{2}) area of membrane?

(a) 0.003 pF (b) 0.01 pF (c) 0.3 pF (d) 4.5 pF (e) 9.5 pF

(a) into the cell (b) out of the cell

(a) 1.0 × 10^{2} (b) 2.3 × 10^{3} (c) 4.4 × 10^{3} (d) 9.1 × 10^{3} (e) 1.8 × 10^{5}

Shown here is a map of equipotential lines for two charges, Q1 and Q2. Potential values are accurate and given in volts.

What is the sign on the charge Q1?

(a) positive (b) negative

(a) |Q1| > |Q2| (b) |Q1| = |Q2| (c) |Q1| < |Q2|

(a) W = -6 μJ (b) W = -2 μJ (c) W = 0 μJ (d) W = 2 μJ (e) W = 6 μJ

(a) 1/4 (b) 1/2 (c) 1 (d) 2 (e) 4