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Electricity and Magnetism Practice Exam for AP Physics C

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By — McGraw-Hill Professional
Updated on Feb 14, 2011

Below is a electricity and magnetism practice exam for AP Physics C exam.  There are two sections in this practice exam.  Section I has 35 multiple choice questions.  Section II has 3 free response questions.  For a thorough review of the concepts in this practice exam, refer to the information center on AP Physics Notes.

If you are taking both AP Physics C exams, the mechanics practice exam can be found at:  Mechanics Practice Exam for AP Physics C

Problems

Multiple Choice Questions

Time: 45 minutes. You may refer to the Constants sheet. However, you may not use the Equations sheet, and you may not use a calculator on this portion of the exam.

  1. Experimenter A uses a very small test charge qo, and experimenter B uses a test charge 2qo to measure an electric field produced by two parallel plates. A finds a field that is
    1. greater than the field found by B
    2. the same as the field found by B
    3. less than the field found by B
    4. either greater or less than the field found by B, depending on the accelerations of the test charges
    5. either greater or less than the field found by B, depending on the masses of the test charges
  2. A solid conducting sphere has radius R and carries positive charge Q. Which of the following graphs represents the electric field E as a function of the distance r from the center of the sphere?
  3. Physics C—Electricity and Magnetism Practice Exam—Multiple-Choice Questions

    Physics C—Electricity and Magnetism Practice Exam—Multiple-Choice Questions

  4. An electron moving at constant velocity enters the region between two charged plates, as shown above. Which of the paths above correctly shows the electron's trajectory after leaving the region between the charged plates?
    1. A
    2. B
    3. C
    4. D
    5. E
  5. Two isolated particles, A and B, are 4 m apart. Particle A has a net charge of 2Q, and B has a net charge of Q. The ratio of the magnitude of the electric force on A to that on B is
    1. 4:1
    2. 2:1
    3. 1:1
    4. 1:2
    5. 1:4
  6. Physics C—Electricity and Magnetism Practice Exam—Multiple-Choice Questions

  7. A uniform electric field points to the left. A small metal ball charged to –2 mC hangs at a 30° angle from a string of negligible mass, as shown above. The tension in the string is measured to be 0.1 N. What is the magnitude of the electric field? (sin 30° = 0.50; cos 30° = 0.87; tan 30° = 0.58).
    1. 25 N/C
    2. 50 N/C
    3. 2500 N/C
    4. 5000 N/C
    5. 10,000 N/C
  8. Physics C—Electricity and Magnetism Practice Exam—Multiple-Choice Questions

  9. A thin semicircular conductor of radius R holds charge +Q. What is the magnitude and direction of the electric field at the center of the circle?
  10. Above an infinitely large plane carrying charge density σ, the electric field points up and is equal to σ/2εo. What is the magnitude and direction of the electric field below the plane?
    1. σ/2εo, down
    2. σ/2εo, up
    3. σ/εo, down
    4. σ/εo, up
    5. zero
  11. Physics C—Electricity and Magnetism Practice Exam—Multiple-Choice Questions

  12. Three charges are arranged in an equilateral triangle, as shown above. At which of these points is the electric potential smallest?
    1. A
    2. B
    3. C
    4. D
    5. E
  13. Physics C—Electricity and Magnetism Practice Exam—Multiple-Choice Questions

  14. The diagram shows a set of equipotential surfaces. At point P, what is the direction of the electric field?
    1. left
    2. right
    3. up the page
    4. down the page
    5. either left or right, which one cannot be determined
  15. A metal sphere carries charge Q; a nonconducting sphere of equal size carries the same charge Q, uniformly distributed throughout the sphere. These spheres are isolated from each other. Consider the electric field at the center of the spheres, within the spheres, and outside the spheres. Which of these electric fields will be the same for both spheres, and which will be different?
  16. Under what conditions is the net electric flux through a closed surface proportional to the enclosed charge?
    1. under any conditions
    2. only when the enclosed charge is symmetrically distributed
    3. only when all nearby charges are symmetrically distributed
    4. only when there are no charges outside the surface
    5. only when enclosed charges can be considered to be point charges
  17. Physics C—Electricity and Magnetism Practice Exam—Multiple-Choice Questions

  18. A hollow metal ring of radius r carries charge q. Consider an axis straight through the center of the ring. At what point(s) along this axis is/are the electric field equal to zero?
    1. only at the center of the ring
    2. only at the center of the ring, and a very long distance away
    3. only a very long distance away
    4. only at the center of the ring, a distance r away from the center, and a very long distance away
    5. everywhere along this axis
  19. Physics C—Electricity and Magnetism Practice Exam—Multiple-Choice Questions

  20. A parallel plate capacitor consists of identical rectangular plates of dimensions a × b, separated by a distance c. To cut the capacitance of this capacitor in half, which of these quantities should be doubled?
    1. a
    2. b
    3. c
    4. ab
    5. abc
  21. Two identical capacitors are hooked in parallel to an external circuit. Which of the following quantities must be the same for both capacitors?
    1. the charge stored on the capacitor
    2. the voltage across the capacitor
    3. the capacitance of the capacitor
    1. I only
    2. II only
    3. II and III only
    4. I and III only
    5. I, II, and III
  22. A 2-μF capacitor is connected directly to a battery. When the capacitor is fully charged, it stores 600 μC of charge. An experimenter replaces the 2-μF capacitor with three 18-μF capacitors in series connected to the same battery. Once the capacitors are fully charged, what charge is stored on each capacitor?
    1. 100 μC
    2. 200 μC
    3. 600 μC
    4. 1200 μC
    5. 1800 μC
  23. A spherical conductor carries a net charge. How is this charge distributed on the sphere?
    1. The charge is evenly distributed on the surface.
    2. The charge resides on the surface only; the distribution of charge on the surface depends on what other charged objects are near the sphere.
    3. The charge moves continually within the sphere.
    4. The charge is distributed uniformly throughout the sphere.
    5. The charge resides within the sphere; the distribution of charge within the sphere depends on what other charged objects are near the sphere.
  24. Physics C—Electricity and Magnetism Practice Exam—Multiple-Choice Questions

  25. Three resistors are connected to a battery as shown in the diagram above. The switch is initially open. When the switch is closed, what happens to the total voltage, current, and resistance in the circuit?
  26. Physics C—Electricity and Magnetism Practice Exam—Multiple-Choice Questions

  27. In the circuit shown above, the 0.5 F capacitor is initially uncharged. The switch is closed at time t = 0. What is the time constant (the time for the capacitor to charge to 63% of its maximum charge) for the charging of this capacitor?
    1. 5 s
    2. 10 s
    3. 20 s
    4. 30 s
    5. 40 s
  28. Physics C—Electricity and Magnetism Practice Exam—Multiple-Choice Questions

  29. In the circuit shown above, what is the current through the 3 Ω resistor?
    1. 0 A
    2. 0.5 A
    3. 1.0 A
    4. 1.5 A
    5. 2.0 A
  30. A light bulb rated at 100 W is twice as bright as a bulb rated at 50 W when both are connected in parallel directly to a 100-V source. Now imagine that these bulbs are instead connected in series with each other. Which is brighter, and by how much?
    1. The bulbs have the same brightness.
    2. The 100-W bulb is twice as bright.
    3. The 50-W bulb is twice as bright.
    4. The 100-W bulb is four times as bright.
    5. The 50-W bulb is four times as bright.
  31. Physics C—Electricity and Magnetism Practice Exam—Multiple-Choice Questions

  32. A uniform magnetic field B is directed into the page. An electron enters this field with initial velocity v to the right. Which of the following best describes the path of the electron while it is still within the magnetic field?
    1. It moves in a straight line.
    2. It bends upward in a parabolic path.
    3. It bends downward in a parabolic path.
    4. It bends upward in a circular path.
    5. It bends downward in a circular path.
  33. Physics C—Electricity and Magnetism Practice Exam—Multiple-Choice Questions

  34. Wire is wound around an insulated circular donut, as shown above. A current I flows in the wire in the direction indicated by the arrows. The inner, average, and outer radii of the donut are indicated by r1, r2, and r3, respectively. What is the magnitude and direction of the magnetic field at point P, the center of the donut?
  35. Physics C—Electricity and Magnetism Practice Exam—Multiple-Choice Questions

  36. A wire carries a current toward the top of the page. An electron is located to the right of the wire, as shown above. In which direction should the electron be moving if it is to experience a magnetic force toward the wire?
    1. into the page
    2. out of the page
    3. toward the bottom of the page
    4. toward the top of the page
    5. to the right
  37. Which of the following statements about electric and magnetic fields is FALSE:
    1. A charge moving along the direction of an electric field will experience a force, but a charge moving along the direction of a magnetic field will not experience a force.
    2. All charges experience a force in an electric field, but only moving charges can experience a force in a magnetic field.
    3. A positive charge moves in the direction of an electric field; a positive charge moves perpendicular to a magnetic field.
    4. All moving charges experience a force parallel to an electric field and perpendicular to a magnetic field.
    5. A negative charge experiences a force opposite the direction of an electric field; a negative charge experiences a force perpendicular to a magnetic field.
  38. Which of these quantities decreases as the inverse square of distance for distances far from the objects producing the fields?
    1. the electric field produced by a finite-length charged rod
    2. the electric field produced by an infinitely long charged cylinder
    3. the electric field produced by an infinite plane of charge
    4. the magnetic field produced by an infinitely long straight current carrying wire
    5. the magnetic field produced by a wire curled around a torus
  39. A proton enters a solenoid. Upon entry, the proton is moving in a straight line along the axis of the solenoid. Which of the following is a correct description of the proton's motion within the solenoid?
    1. The proton will be bent in a parabolic path.
    2. The proton will be bent in a circular path.
    3. The proton will continue in its straight path at constant velocity.
    4. The proton will continue in its straight path and slow down.
    5. The proton will continue in its straight path and speed up.
  40. Physics C—Electricity and Magnetism Practice Exam—Multiple-Choice Questions

  41. A uniform magnetic field points into the page. Three subatomic particles are shot into the field from the left-hand side of the page. All have the same initial speed and direction. These particles take paths A, B, and C, as labeled in the diagram above. Which of the following is a possible identity for each particle?
  42. Physics C—Electricity and Magnetism Practice Exam—Multiple-Choice Questions

  43. The electric dipole shown above consists of equal-magnitude charges and has an initial leftward velocity v in a uniform magnetic field pointing out of the page, as shown above. The dipole experiences
    1. a clockwise net torque, and a net force to the left
    2. a counterclockwise net torque, and a net force to the left
    3. no net torque, and a net force to the left
    4. a counterclockwise net torque, and no net force
    5. a clockwise net torque, and no net force
  44. A beam of electrons has speed 107 m/s. It is desired to use the magnetic field of the Earth, 5 × 10–5 T, to bend the electron beam into a circle. What will be the radius of this circle?
    1. 1 nm
    2. 1 μm
    3. 1 mm
    4. 1 m
    5. 1 km
  45. A very small element of wire of length dL carries a current I. What is the direction of the magnetic field produced by this current element at point P, shown above?
    1. to the right
    2. toward the top of the page
    3. into the page
    4. out of the page
    5. there is no magnetic field produced at point P by this element.
  46. Physics C—Electricity and Magnetism Practice Exam—Multiple-Choice Questions

  47. A loop of wire surrounds a hole in a table, as shown above. A bar magnet is dropped, north end down, from far above the table through the hole. Let the positive direction of current be defined as counterclockwise as viewed from above. Which of the following graphs best represents the induced current I in the loop?
  48. A rectangular loop of wire has dimensions a × band includes a resistor R. This loop is pulled with speed v from a region of no magnetic field into a uniform magnetic field B pointing through the loop, as shown above. What is the magnitude and direction of the current through the resistor?
    1. Bav/R, left-to-right
    2. Bbv/R, left-to-right
    3. Bav/R, right-to-left
    4. Bbv/R, right-to-left
    5. Bba/R, right-to-left
  49. Physics C—Electricity and Magnetism Practice Exam—Multiple-Choice Questions

  50. A conducting wire sits on smooth metal rails, as shown above. A variable magnetic field points out of the page. The strength of this magnetic field is increased linearly from zero. Immediately after the field starts to increase, what will be the direction of the current in the wire and the direction of the wire's motion?
  51. Physics C—Electricity and Magnetism Practice Exam—Multiple-Choice Questions

  52. A uniform magnetic field B points parallel to the ground. A toy car is sliding down a frictionless plane inclined at 30°. A loop of wire of resistance R and cross-sectional area A lies in the flat plane of the car's body, as shown above. What is the magnetic flux through the wire loop?
    1. zero
    2. BA cos 30°
    3. BA cos 60°
    4. BA
    5. (BA cos 60°)/R
  53. Physics C—Electricity and Magnetism Practice Exam—Multiple-Choice Questions

  54. If the two equal resistors R1 and R2 are connected in parallel to a 10-V battery with no other circuit components, the current provided by the battery is I. In the circuit shown above, an inductor of inductance L is included in series with R2. What is the current through R2 after the circuit has been connected for a long time?
    1. zero
    2. (1/4) I
    3. (1/2) I
    4. I

STOP. End of Physics C—Electricity and Magnetism Practice Exam—Multiple-Choice Questions

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