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 82. The exam period was 75 minutes; the mean score was 62.8; the median was 62. 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}.

An electron (mass 9.11 × 10^{-31} kg, charge 1.6 × 10^{-19} C) moves rightward at speed 10^{5} m/s as it passes from a field-free region into a region where there is a magnetic field of strength B = 0.03 T. Shortly thereafter, it exits, moving leftward back into the region where B = 0.

Find L, the distance between where the electron entered the field and where it exited the field.

(a) 22 μm (b) 26 μm (c) 32 μm (d) 38 μm (e) 44 μm

(a) 0.38 ns (b) 0.6 ns (c) 1.2 ns

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

Consider two parallel wires, one carrying current I_{1} = 20 A to the right, and at a distance L = 8 cm below it, another carrying I_{2} = 12 A to the left.

What is the magnetic field a distance 5 cm below the top wire (3 cm above the bottom one)?

(a) 1.6 × 10^{-4} T, out of page (b) 8.0 × 10^{-5} T, out of page (c) 0 (d) 8.0 × 10^{-5} T, into page (e) 1.6 × 10^{-4} T, into page

(a) 3.6 × 10^{-5} N (b) 4.8 × 10^{-5} N (c) 6 × 10^{-5} N

(a) yes, they attract each other (b) no, they do not attract each other

The phasor diagram shown applies to a certain RLC circuit at some particular frequency. Note that the lengths of three vectors are labeled in volts.

At the instant shown, the voltage across the capacitor is increasing.

(T) True (F) False

(a) Z = 4 Ω (b) Z = 5 Ω (c) Z = 7.8 Ω (d) Z = 9 Ω (e) Z = 9.2 Ω

(a) 0.13 H (b) 0.2 H (c) 0.3 H

(a) 16.8 V (b) 22.6 V (c) 23.7 V (d) 30.5 V (e) 32 V

The solenoid shown has a radius of 3 cm and 200 turns of wire along an 18 cm axis.

What constant current would be required to produce a magnetic field B = 0.01 T in the interior of this solenoid?

(a) 7.2 A (b) 43 A (c) 240 A

(a) 4.2 × 10^{-8} V (b) 8.5 × 10^{-8} V (c) 1.7 × 10^{-7} V

A bar is free to slide along a pair of metal tracks separated by a distance of L = 28 cm. (You may ignore friction between the bar and the tracks.) At one end, the tracks are connected electrically by a resistor R = 3.9 Ω. You should assume the metal bar completes an electric circuit. A magnetic field B = 0.15 T points into the page.

If the bar is moving to the left at 8 m/s, what current flows through the resistor?

(a) 86 mA (b) 150 mA (c) 336 mA

(a) 0.8 m/s (b) 2 m/s (c) 15 m/s (d) 140 m/s (e) 730 m/s

(a) upward (b) downward

In this RLC circuit, R = 180 Ω, L = 22 mH, and C = 4.7 μF. A function generator whose operating frequency can be adjusted applies an alternating voltage.

Suppose the maximum generator voltage V_{max} = 20 V when f = 290 Hz. What rms current flows through this circuit?

(a) 0.07 A (b) 0.1 A (c) 0.15 A

(again assuming f = 290 Hz)?

(a) 8.6 × 10^{-3} Ω (b) 120 Ω (c) 860 &Omega

(a) It glows most brightly at f = 290 Hz. (b) Must reduce frequency to make it glow brighter. (c) Must increase frequency to make it glow brighter.

Three turns of wire are wound in a square of side 41 cm. The wire itself has negligible resistance, but completes a circuit across an external resistance of 12 Ω. By connecting the loop to a regulated motor, you can get it to spin at a constant angular frequency in a magnetic field of strength B = 0.9 T. (The magnetic field points out of the page, as shown). At the instant shown, the loop lies in a plane perpendicular to the magnetic field, with the right side of the wire loop moving out of the page. The maximum current is observed to be 100 mA, though not necessarily at the instant shown.

What torque does the magnetic field exert on the loop when the current I = 100 mA?

(a) 1.0 × 10^{-3} Nm (b) 2.1 × 10^{-3} Nm (c) 1.8 × 10^{-2} Nm (d) 4.5 × 10^{-2} Nm (e) 2.1 × 10^{-1} Nm

(a) 2.6 rad/sec (b) 3.3 rad/sec (c) 7.6 rad/sec (d) 5.1 rad/sec (e) 7.9 rad/sec

(a) At that instant, current will flow down along that side. (b) At that instant, current will flow upward along that side. (c) At that instant, no current flows in the loop.n