1. Each plate of a capacitor stores a chargc of magnitude 1.0 mC when a 100 V potential difference is applied. The capacitance is:
A) 5µF
B) 10 pF
C) SO pF
D) 100
E) None of the above
2. If the charge on a parallel-plate capacitor is doubled:
A) The capacitance is halved.
B) The capacitance is doubled.
C) The electric field is halved.
D) The electric field is doubled.
E) The surface charge density is not changed on either plate.
3. A parallel-plate capacitor has a plate area of 0.2 m2 and a plate separation of 0.1 mm. If the charge on each plate has a magnitude of 4 pC, the potential difference across the plates is approximately:
A) 0 V
B) 4x10-V
C) 3x10. V
6) 4x10V
4. Each of the four capacitors have a capacitance of 500 pF. The voltmeter reads 1000 V
The magnitude of the charge on each capacitor plate is:
A) 0.2 C
B) 0.5C
C) 20 C
D) 50 C
E) None of the above
5. A certain parallel-plate capacitor has a capacitance of 10 pF. After it is charged to 5 pC and isolated, the plates arc pulled apart so its capacitance becomes 5 pF. The work done by the external agent is about:
A) Zero
B) +1.25 pJ
C) -1.25µJ
D) +0.83 pJ
E) -0.83µJ
6. What is the magnitude of the charge stored on each plate of the 4 pF capacitor in the circuit ?
A) 12 pC
B)18 pC
C)36 pC
D)96 pC
E)116 pE
7. What happens to the atoms in a dielectric when it is placed between the plates of a charged capacitor?
A) They begin to conduct electricity.
B) They create an induced electric field that is in the opposite direction of the field due to the charges on the plates.
C) They create an induced electric field that is in the same direction as the field due to the charges on the plates.
D) The completely cancel the electric field due to the charges on the plates.
E) They rotate so their positive ends are toward the positively charged plates.
8. The diagram shows four 6 pF capacitors. The capacitance (in pF) between points a and b is
(A) 3
(B) 4
(C) 6
(D) 99.
9. Three wires arc made of the same material and have the same length. The cross sections are circle, square and diamond-shaped (90° inner angle) as shown in the figures below. Rank the resistances from largest to smallest.
A) 1,2,3
B) 1,3,2
C) 2, 1, 3
D) 2, 3, 1
E) 3, 1, 2
10. The free electron drift velocity in a uniform wire is 1.00 cm/s. The resistivity of the wire is 1.72x 10-811 • m and the electric field inside the wire is 1.00x10-4 V/m. The free electron number density is:
A) 3.63x101° cm-3
B) 3.63x1025 cm-3
C) 3.63x1023 cm-3
D) 3.63x1031 cm-3
E) 3.63x1024 cm-3
11. The current in a wire as a function of time is shown in the following figure. From t = 0 min to t = 1 min. how much charge passes through the cable?
A) 10 C
B) 20 C
C) 30 C
D) 40 C
E) SO C
12. A certain resistor dissipates 0.5 W when connected to a 3 V potential difference. When connected to a 1 V potential difference, this resistor will dissipate:
(A) 0.056 W (B) 0.167 W (C) 1.5 W (D) 0.56 W (E) none of these
13. To make a longer cable in an experiment, three wires of differing materials but identical length and cross-section are connected together end-to-end. The materials are silver, aluminum, and iron with resistivitics
1.59x10-8R • m, 2.65x10-8 It • m, and 9.71x 10-0 ft • m respectively. The potential along this long cable relative to ground is plotted below. Identify the materials for each wire segment, from left to right:
A) Silver, aluminum, iron
B) Silver, iron, aluminum
C) Iron, silver, aluminum
D) Iron, aluminum, silver
E) Aluminum, iron, silver
14. The heating element inside an electric kettle has a resistance of 2011 and is plugged into a 110 V source.
2.0x 105 J of energy is needed for the water in the kettle to boil. If the all of the power dissipated in the heating clement is converted to heat, how long will it take for the water to boil?
A) 5.5 min
B) 330 min
C) 10 min
D) 12 min
E) 120 min
15. A variable resistor in the form of a uniform conducting ring as shown below. The positive terminal of a battery is connected at point 0. Where should the negative terminal be connected to get the largest current i through the upper portion of the ring? Where should it be connected to get the smallest current?
A) Largest at 1, smallest at 2
B) Largest at 2, smallest at 2
C) Largest at 1, smallest at 3
D) Largest at 2, smallest at 3
E) Largest at 3, smallest at 1
16. An electron (-e) is moving eastward, and a proton (+e) is moving westward. Both particles pass through a
surface within a time period of 2 seconds. What is the average current through this surface during this time?
A) Zero
B) 0.4x10 -19A
C) 0.8x10 -19A
D) 1.6x10 -19A
E) 3.2x10 -19A
17. In the diagram below, Rs = R2 = R3 = 3R and Rs = 2R. If equal currents pass through R4 and Rs, what is the value of R4?
A) R
B) 2R
C) R/2
D) 3R/2
E) None of the above
18. Wires A, B, C, D, E mcct at a junction. Wires A, C and E carry 2 A, 3 A and 5 A respectively into the
junction, while wire D carries 7 A out of the junction. How much current (with respect to the junction) does wire B carry?
A) 2 A in
B) 2 A out
C) 3 A in
D) 3 A out
E) None of the above
19. The part of a circuit shown below has a net input current i = 1.5 A in the direction shown. The resistors R1,
R2, R3, and R4 are 1 11, 2 11, 3 11, and 411 respectively. The ammeter has negligible resistance. What is the current recorded by the ammeter?
A) 0.1 A
B) 0.2 A
C) 0.3 A
D) 0.4 A
E) None of the above
20. A resistor with resistance R1 and a resistor with resistance R2 are connected in parallel to an ideal battery with cmf E. The rate of thermal energy generation in the resistor with resistance RI is:
A) E2/R1
B) E2/21/(R1 + R2)2
C) E2/(R1 + R2)
D) EvRz
E) E2R1/R1
21. The equivalent resistance between points I and 2 of the circuit shown is:
A) 2.5(Ω
B) 4.0(Ω
C) 5.0(Ω
D) 6.5(Ω
E) 16 (Ω
22. In the diagrams, all light bulbs arc identical and all emf devices are identical. In which circuit will the bulbs be dimmest?
23. In an antique automobile, a 6 V battery supplies a total of 48 W to two identical headlights in parallel. The resistance of each bulb is:
A) 0.7511
B) 1.511
C) 3.011
D) 4.011
E) 8.011
24. An electron moves through a uniform magnetic field given by B = Bx I + 3Bx j. At a particular instant, the electron has velocity v = 2 m/s 1 + 4 m/s j and the magnetic force acting on it is F = 6.4x 10-19 N k. is equal to:
A) +2.0 T
B) -2.0 T
C) +0.3 T
D) -0.3 T
E) Zero
25. A thin copper rod 1.0 m long has a mass of 0.050 kg and is in a magnetic field of 0.10 T. What minimum current in the rod is needed in order for the magnetic force to cancel the weight of the rod?
A) 1.2 A
B) 2.5A
C) 4.9 A
D) 9.8 A
E) 0.6 A
USEFUL CONSTANTS:
Acceleration due to gravity, g = 9.8 m/s2; Coulomb constant, Ir. = 8.99 x 109 N.m2/C2; Permittivity of free space, e.= 8.85 x 10-12 c2/N ja2; Speed of light in vacuum c = 3.00 x 108 m/s
|
Particle
|
Mass (kg)
|
Charge (C)
|
|
Electron
|
9.11 x 10-31
|
-1.6 x 10-19
|
|
Proton
|
1.67 x 10-21
|
+1.6 x 10-19
|
28. A positively charged particle of q = 2 C moves upward into a region whom both a magnetic field B directed out of the page and an electric field E directed left are acting as shown in the figure. The magnetic field has a magnitude of B = 4.0x10-4 T and the electric field has a magnitude of E = 0.1 N/C. At what velocity v must the particle be moving if it is not deflected when it enters this area?
A) 4x10-3 m/s
B) 125 m/s
C) 250 m/s
D) 500 m/s
E) The particle will be deflected to the left regardless of its velocity.
29. A wire 50 cm long carries a 0.5 A current in the positive direction of an x-axis througn a magnetic ncia B = 3 mT j + 10 mT k. In unit vector notation, what is the magnetic force on the wire?
A) -2.5 mN j + 0.75 mN k
B) +2.5 mN j - 0.75 mN k
C) -0.75 mN j + 2.5 mN k
D) +0.75 mN j - 2.5 mN k
E) Zero
30. Two concentric, circular wire loops, of radii r1 = 20 cm and r2 = 30 cm, are located in the xy-plane; each carrying a clockwise current of 7 A as shown in the figure. The magnitude of the net magnetic dipole moment of the system is
A) 1.1 A • m2
B) 2.06 A • m2
C) 10.5 A • m2
D) 21 A • m2
E) Zero
