SparkNotes: Review of Magnetic Forces and Fields: Test

1. All magnetic fields are caused by

(A) Compasses

(B) Permanent Magnets

(C) Moving charges

(D) None of the above

2. Two wires running parallel to each other experience

(A) A mutual repulsion

(B) A mutual attraction

(C) No force

(D) Depends on the magnitude of the currents

3. Two wires running perpendicular to each other experience

(A) A mutual repulsion

(B) A mutual attraction

(C) No force

(D) Depends on the magnitude of the currents

4. Two wires running anitparallel to each other experience

(A) A mutual repulsion

(B) A mutual attraction

(C) No force

(D) Depends on the magnitude of the currents

5. Einstein derived relativity from

(A) Electric theory

(B) Magnetic theory

(C) Quantum Mechanics

(D) Thermodynamics

6. The force on a moving charge in the presence of a magnetic field is always

(A) Perpendicular to both the charge's velocity and the magnetic field

(B) Parallel to the charge's velocity

(C) Parallel to the magnetic field

(D) None of the above

7. The force on a moving charge in a magnetic field is always proportional to

(A) The speed of light

(B) The angle between the velocity of the charge and the magnetic field

(C) The velocity of the charge

(D) None of the above

8. The force on a moving charge parallel to a magnetic field is always

(A) Positive

(B) Negative

(C) Zero

(D) Parallel to the magnetic field

9. The force on a charge moving perpendicular to a magnetic field is given by

(A) F =

(B) F =

(C) F =

(D) F =

10. The force on a wire moving perpendicular to a magnetic field is given by

(A) F =

(B) F =

(C) F =

(D) F =

11. The force on a charge moving at some angle θ to a magnetic field is proportional to

(A) θ

(B) cosθ

(C) sinθ

(D) tanθ

12. The total work done by a magnetic field on a moving charge is always

(A) Positive

(B) Negative

(C) Zero

(D) Depends on the situation

13. The net charge on a wire carrying a current I is

(A) 0

(B) I

(C) - I

(D) I²

14. The magnetic force is always

(A) Perpendicular to the electric force

(B) Parallel to the electric force

(C) Antiparallel to the electric force

(D) Depends on the situation

15. All magnets have

(A) A north pole

(B) A south pole

(C) An east pole

(D) Both a north and south pole

16. A compass measures

(A) Electric Field

(B) Magnetic Field

(C) Electric Force

(D) Magnetic Force

17. The point on the compass of a needle near a current carrying wire always points

(A) Towards the wire

(B) Away from the wire

(C) Parallel to the wire

(D) Perpendicular to the wire

18. The magnetic field caused by a wire with current I is:

(A) B =

(B) B =

(C) B =

(D) B =

19. Magnetic field lines near straight wires are always

(A) Straight lines

(B) Ellipses

(C) Circles

(D) None of the above

20. The force, per unit length, between two parallel current carrying wires is defined as

(A) F =

(B) F =

(C) F =

(D) F =

21. The unit of magnetic field, in CGS units, is

(A) Tesla

(B) Gauss

(C) Ampere

(D) Volt

22. The magnitude of the magnetic field at a point P caused by a small length of wire, dl, at an angle θ to the vector from dl to P is given by

(A) dB = Idlr cosθ

(B) dB = Idlr sinθ

(C) dB = Idl sinθ

(D) dB = I²dlr cosθ

23. What is the magnitude of the magnetic field of a wire carrying a current of 6×10¹⁰ esu/sec, at a distance of 2 cm from the wire?

(A) 1

(B) 2

(C) 3

(D) 4

24. A ring of wire carrying a current creates what kind of magnetic field?

(A) Uniform magnetic field

(B) Circular magnetic field

(C) Straight magnetic field

(D) None of the above

25. On the axis of a current carrying ring of radius b, at what point is the magnetic field maximum?

(A) z = b

(B) z = 0

(C) z = - b

(D) z = πb

26. A ring of radius 2 cm carries a current of 3×10¹⁰ esu/sec. What is the strength of the magnetic field at the center of the ring?

(A) 1

(B) 2

(C) π

(D) 2π

27. The field inside a long solenoid can be approximated as

(A) Circular

(B) Uniform

(C) The field of a single ring

(D) None of the above

28. The magnetic field inside a solenoid is maximum

(A) At one of the ends

(B) At the center

(C) Outside the solenoid

(D) None of the above

29. A solenoid of length 1,000 cm has 2,000 turns carrying a current of 6×10¹⁰ esu/sec. Because it is so long, it can be approximated near the center as an infinite solenoid. What is the magnetic field strength at the center of the solenoid?

(A) 16, 000π

(B) 8, 000π

(C) 16π

(D) 8π

30. A current carrying wire is placed along the axis of a long solenoid. In what direction does the force on the wire point?

(A) Along the axis of the solenoid

(B) Perpendicular to the axis of the solenoid

(C) Tangential to the wire

(D) There is no force

31. The field along the axis of an infinitely long solenoid is given by

(A)

(B)

(C)

(D)

32. The first right hand rule is used to determine

(A) The magnetic field of a wire

(B) The magnetic field of a solenoid

(C) The force on a charge in a magnetic field

(D) None of the above

33. The second right hand rule is used to determine

(A) The magnetic field of a wire

(B) The magnetic field of a solenoid

(C) The force on a charge in a magnetic field

(D) None of the above

34. A ring and an infinite solenoid both have the same radius and current. Which one produces a stronger magnetic field on its axis?

(A) The ring

(B) The solenoid

(C) Both produce the same field

(D) Depends on the situation

35. The divergence of a vector field at a given point is

(A) A vector

(B) A vector field

(C) A scalar

(D) A function

36. What is the divergence of the field (2x, 2y, 2x)?

(A) 6

(B) 4

(C) 2

(D) 0

37. What is the divergence of the field (x², x + y, z)?

(A) 2

(B) 3

(C) 2x

(D) 2x + 2

38. Gauss' theorem relates

(A) Line integrals and surface integrals

(B) Line integrals and volume integrals

(C) Surface integrals and volume integrals

(D) Two surface integrals

39. Gauss' theorem only applies to

(A) Closed loops

(B) Closed surfaces

(C) Functions with zero divergence

(D) Functions with zero curl

40. The curl of a vector field at a given point is

(A) A vector field

(B) A vector

(C) A scalar

(D) A function

41. The curl measures

(A) The direction of flow of a vector field

(B) The amount and direction of rotation in a vector field

(C) The magnitude of the vector field at a given point

(D) None of the above

42. What is the curl of (2x, 2y, 2z)?

(A) (2, 2, 2)

(B) (2, 0, 2)

(C) (1, 1, 1)

(D) (0, 0, 0)

43. Stokes' Theorem relates

(A) Line integrals and surface integrals

(B) Line integrals and volume integrals

(C) Surface integrals and volume integrals

(D) Two surface integrals

44. The line integral around any closed loop in an electric field is equal to

(A)

(B) 4πQ

(C) 0

(D) qE

45. The line integral around any closed loop in a magnetic field is equal to

(A)

(B) 4πQ

(C) 0

(D) qE

46. The curl of any magnetic field is

(A) 0

(B) Proportional to the current in the field

(C) Proportional to the current density at a given point

(D) Proportional to the total charge in the field

47. The divergence of any magnetic field is

(A) 0

(B) Proportional to the current in the field

(C) Proportional to the current density at a given point

(D) Proportional to the total charge in the field

48. The fact about the divergence in a magnetic field is due to

(A) The curl of the magnetic field

(B) The absence of magnetic charge

(C) The nature of electric currents

(D) The nature of magnetic currents

49.

Jda is equal to

(A) B

(B) c

(C) I

(D) V

50. How many licks does it take to get to the center of a tootsie roll pop?

(A)

(B)

(C) The divergence of the tootsie roll pop

(D) Ask the owl