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### Question limit

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### 78 Multiple choice questions

1. Because AC current changes direction, the____ and____ in an AC circuit is not constant
2. Most power plants use a source of _____ to turn a turbine in a magnetic field to generate current.
3. ___performed experiments that generated and detected EM waves and confirmed Maxwell's predictions.
4. The motor's magnetic field generates its own emf called ___
5. ∆V2/∆V1 = N2/N1
6. add rings (slip rings) and brushes to the end of the loops, the moving rings counter the changing current and create direct current for a circuit
7. Only the portion of the magnetic field____ to the wire will induce current in it
8. Oscillating electric and magnetic fields create
9. current runs through the 2nd coil because it is wrapped around magnetized iron
10. An decrease in emf means an____ in current
11. Electromagnetic waves transfer____ - stored in the oscillations of the electric and magnetic fields
12. When you have multiple loops, you multiple the number of loops (N) by the ____
13. Electromagnetic force obeys the ____ - as the two objects move further apart the force between them weakens
14. As the loop rotates from one arm being up to the other being up, the current flow will change direction - producing ____
15. emf = -∆ϕM/∆t
16. decreases the emf, N2is less than N1
17. A device that increases or decreases the emf of alternating current
18. convert electrical energy to mechanical energy
19. The magnetic field force pushes the___ through the wire
20. Induced current is greatest if the wire and magnetic field are_____ to each other
21. A particle of light is called a____ - carries energy, but has no mass
22. "The magnetic field of an induced current is in a direction to produce a field that oppose the change causing it"
23. when the armature is parallel to the magnetic field in a generator, you get ____
24. The induced field does not oppose applied field, but the____ in the applied field
25. N∆ϕM/∆t
26. As the magnetic field approaches the wire, the wire's magnetic field is in the____ direction of the increasing magnetic field
27. if the angle is zero the wire is____ to the magnetic field
28. Either the ____ can move in the magnetic field or the field can move around the ____ - one or the other must move to induce current.
29. motion of _____ through a wave makes it move
30. If the applied field changes, the _____ helps to keep it constant
31. Notion that EM waves behave like particles is called the____
32. Electric and magnetic forces are aspects of a ____ - called electromagnetic force
33. emf = NAβω
34. The current induced in the wire by moving through a magnetic field will generate its own _______
35. ____ in the engine is a transformer that increases this emf to a great enough value to cause a spark between the gaps of a spark plug
36. __ depends on the shape of the coils and how they are orientated to each other
37. electromagnetic waves are ___
38. A generator produces changing____, because of its constant rotating
39. Separation of charges by magnetic force will induce ____in the wire
40. three ways to induce current
41. Current can also be generated in a magnetic field by changing the_____ of the loop in the magnetic field
42. increases the emf, N2 is greater than N1
43. Energy transported by EM waves is called ____
44. The increase in emf means a____ in current
45. Current is supplied to loops and that magnetic field repels ______ and causes the loops to rotate
46. current in this coil magnetizes the iron core
47. ____ increases as the magnitude of the magnetic field changes at a higher rate
48. producing current in a wire by placing it in a changing magnetic field
49. ____ is the ability of one circuit to induce emf in a nearby circuit in the presence of a changing magnetic field
50. when the armature is perpendicular to the magnetic field in a generator, you get____
51. is the angular speed of rotation of the loop (2πf)
52. Changing the ___ of the loops of wire or _____ the loop in the magnetic field will change the amount of induced current
53. emf = - M(∆I/∆t)
54. As the coil moves out of the magnetic field the induced field is in the_____ direction as the original and they attract each other
55. Low-energy photons behave more like ___
56. Effective ___ and effective ____ are the average values in the AC circuit - called Irms
57. The induced magnetic field is similar to a _____- and creates a force that repels the original magnetic field
58. is the mutual inductance of the two-coil system
59. In the US, power companies step-up emf to about ____
60. _____ are only 90-99% efficient - power is lost due to small currents induced by changing magnetic field and resistance in the wires
61. ____created a set of equations that explain the relationship between electric and magnetic fields
62. All EM waves are produced by ____ - a charge moves up/down through the wave at a certain frequency
63. As a motor turns more quickly, the net emf and net current in the coil___
64. The____ of rotation of the loop in a generator will determine how often the current changes direction -> f = 60Hz in US
65. emf unit is the
66. who first demonstrated the principle of electromagnetic induction
67. Some high energy EM waves will behave like____
68. Maxwell predicted that light was ___-
69. Use the ___ right hand rule to figure out the direction of current flow in the wire
70. Changing the____ of coils in the secondary coil can change the induced emf in the secondary coil - used in making transformers
71. Magnitude of emf depends on (3):
72. tells the direction of the induced emf
73. You can use ____ to find resistance
74. High-energy photons behave more like____
75. The _____ supplied to the motor equals the applied emf minus the back emf, this also reduces current
76. Car batteries provide a constant DC emf of ___
77. Oscillating Electric and Magnetic waves - at___ angles to each other
78. Predicts the magnitude of induced emf