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 101. The exam period was 90 minutes; the mean score was 75.4; the median was 78. Click here to see page1 page2 of the formula sheet that came with the exam.

Four charges rest at the four corners of a rectangle with sides d and 2d. Two charges are positive and two charges are negative. (q = 2 C, d = 10 cm)

The electric potential is the same along the entire y-axis as it is in the center (point A) of the rectangle.

(T) True (F) False

(a) very close to points P_{1}, P_{2}, P_{3} and P_{4} (b) at x = y = 0 (c) at coordinates (x, y) = (0, d/2)

(a) in the y-z plane (at x = 0) (b) in the x-z plane (at y = 0) (c) in the x-y plane (at z = 0)

This and the next question are about the following situation:

Consider a spherical Gaussian surface of radius r centered on a point charge Q, as shown above. As the radius r increases the total electric flux through the Gaussian surface also increases.

(a) charge. (b) surface area to a Gaussian surface. (c) dimensions to space.

An infinitely long, cylindrical conducting wire of radius a has a surface charge density σ (charge/unit area).

What is the magnitude of the electric field, E(r), outside the wire at a radial distance r from the wire's center?

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

(a) parallel to the wire. (b) radially away from the central axis of the wire. (c) radially toward the central axis of the wire.

Two point charges are placed on the x-axis as shown. Let Q = 3 μC and a = 5 m.

The y component of the electric field at point A is zero.

(a) E_{A} / E_{B} = 0 (b) E_{A} / E_{B} = 0.64 (c) E_{A} / E_{B} = 0.80 (d) E_{A} / E_{B} = 1.13 (e) E_{A} / E_{B} = 1.35

The figure below shows three flat plates, all of very large area. The two thin plates are made of insulating material and carry uniformly-distributed surface charge densities of σ_{a} and σ_{b} respectively. The thick metal plate has width w, and is initially uncharged.

What is the magnitude of the electric field E_{A} at the origin (the point marked A on the figure)?

(a) |E_{A}| = 1.4 × 10^{5} N/C (b) |E_{A}| = 2.8 × 10^{5} N/C (c) |E_{A}| = 5.6 × 10^{5} N/C

(a) σ_{LHS} < 0 (b) σ_{LHS} = 0 (c) σ_{LHS} > 0

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

(a) Add negative charge to the metal slab. (b) Add positive charge to the metal slab. (c) Changing the charge on the metal slab will not affect the potential difference ΔV_{ab}.

Two charges, +Q and -Q (equal in magnitude but opposite in sign) are fixed at a distance a from the origin on the x-axis. Point B is located at a distance b from the origin on the y-axis, and point C is located a distance c to the right of the charge +Q.

Now, a charge, q_{3} = +1 μC, is brought in from infinity and placed at point B. The total potential energy of the charge collection

(a) increases. (b) remains unchanged. (c) decreases.

(a) v_{∞} = 33.84 m/s (b) v_{∞} = 0 m/s (c) v_{∞} = 8.25 m/s (d) v_{∞} = 14.41 m/s (e) It does not travel away from the charges.

A point charge Q is located at the center of a thick conducting spherical shell with inner radius a_{1} and outer radius a_{2}. The shell has zero total charge. A thin spherical shell of non-conducting material radius a_{3} with uniform surface charge density surrounds the conductor. The net charge on the non- conductor is Q_{NC}.

Calculate the radial component of the total electric field at a radius 15 cm from the center of symmetry. (In the answer list below, a plus sign denotes a field that points radially outward, a minus sign the opposite direction.)

(a) E = + 7.20 × 10^{6} V/m (b) E = + 4.80 × 10^{6} V/m (c) E = + 3.60 × 10^{6} V/m (d) E = - 2.40 × 10^{6} V/m (e) E = - 5.60 × 10^{6} V/m

(a) σ_{2} = +398 μC/m^{2} (b) σ_{2} = +154 μC/m^{2} (c) σ_{2} = 0 μC/m^{2} (d) σ_{2} = -298 μC/m^{2} (e) σ_{2} = -326 μC/m^{2}

(a) V_{C} = - 6.74 × 10^{5} V (b) V_{C} = - 5.20 × 10^{5} V (c) V_{C} = 0 V (d) V_{C} = + 3.26 × 10^{5} V (e) V_{C} = + 4.50 × 10^{5} V

What is the magnitude of the force on charge Q_{1}?

(a) 6.75 × 10^{-3} N (b) 9.28 × 10^{-3} N (c) 10.06 × 10^{-3} N (d) 11.25 × 10^{-3} N (e) 12.73 × 10^{-3} N

Four capacitors, a battery and a switch are assembled in the circuit below. Initially, the switch is set to position A and C_{4} is uncharged.

Find U, the total energy stored in the capacitors.

(a) U = 14 mJ (b) U = 26 mJ (c) U = 30 mJ (d) U = 45 mJ (e) U = 55 mJ

When the switch is moved from A to B, C_{1} and C_{2} are discharged.

(a) Q_{4} = 83 μC (b) Q_{4} = 162 μC (c) Q_{4} = 200 μC (d) Q_{4} = 222 μC (e) Q_{4} = 320 μC

This figure shows the electric field lines for a system of two point charges, A and B. Three positions, labeled 1,2,3 are also marked.

Which one of the following is correct?

(a) A is positive and smaller in magnitude than B. (b) A is negative and larger in magnitude than B. (c) A is negative and smaller in magnitude than B.

(a) 1 > 2 > 3 (b) 3 > 2 > 1 (c) 2 > 1 > 3