Physics 1240 Ch 12

58. current through a 50 ohm resistor is I=0.8sin(240t). what is the rms current

.57A

30. a 0.20m wire is moved perpendicular to a 0.5 T magnetic field at a speed of 1.5 m/s. what emf is induced across the ends of the wire?

0.15V

25. the magnetic flux through a circular area of a radius 30 cm due to a uniform magnetic field of 1.4 T whose direction makes a 30 degree angle with the plane of the coil is

0.198 Wb

11. an FM radio station generates radio waves that have a frequency of 96.5 MHz The frequency of the waves from a competing station have a frequency of 103.7 MHz. what is the difference in wavelength between the waves emitted from the two stations?

0.2 m

13. a cellular telephone transmits electromagnetic waves at a frequency of 900 MHz. what is the wavelength of these waves?

0.333m

26. a solenoid of 1000 turns is wound on a cardboard cylinder 80 cm long and 2 cm in diameter. when the current falls from 8A to 3A in a 4-ms interval, the induced emf is

0.617 V

57. current through a 50 ohm resistor is I=0.8sin(240t). what is the peak current

0.8A

62. the amount of AC current that produces the same average joule heating effect as ampere of DC current is

1.41 A peak current

55. a 150-W lamp is placed into a 120-V ac outlet. what are the peak and rms currents

1.77A and 1.25 A

60. current through a 50 ohm resistor I=0.8sin(240t). how much power is dissipated in the resistor

16 W

46. the flux through a coil changes from 5x10^-5 Wb to 6x10^-5 Wb in 0.1s. what is the induced emf

1x10^-4 V

32. a coil with a self-inductance of 1.5 mH will show a rate of current change of what value when inducing an emf of 0.30 V

2 x 10^2 A/s

10. when a radio telescope observes a region of space between two stars, it detects electromagnetic radiation due to hydrogen gas that has a wavelength of 0.11m. what is the frequency of this radiation

2.7 x 10^9 Hz

41. a coil of 40 turns and cross-section area 12 cm^2 is oriented perpendicular to a magnetic field, which varies from 0 to 1.2 T in 0.02s. what emf is induced in the coil

2.88V

14. note the different types of electromagnetic radiation: 1-X-rays 2-visible light 3-radio waves 4-infared radiation 5-gamma rays 6-ultraviolet radiation Which list ranks the electromagnetic waves in order of increasing frequency?

3,4,2,6,1,5

54. a circular loop of radius 0.10 m is rotating in a uniform magnetic field of 0.20 T find the magnetic flux through the loop when the plane of a loop and the magnetic field vector are at an angle of 30 degrees

3.1 x10^-3 Tm^2

50. what is the wavelength of a 92.9 MHz radio wave

3.2m

59. current through a 50-ohm resistor is I= 0.8sin(240t). at what frequency does the current vary

38 Hz

31. a planar loop consisting of four turns of wire, each of which encloses 200 cm^2, is oriented perpendicularly to a magnetic field that increases uniformly in magnitude from 10mT to 25mT in a time of 5.0ms. what is the resulting induced current in the coil if the resistance of the coil is 5.0 ohms

48 mA

5. a transformer with 100 turns in the primary coil and 400 turns in the secondary coil will change 120-V ac electricity into ______ ac electricity

480-V

28.a transformer consists of a 500 turn primary coil and a 2000 turn secondary coil. If 120 V is applied to the primary, how many volts will appear across the secondary

480V

37. a flat coil of wire consisting of 20 turns, each with an area of 50 cm^2, is positioned perpendicularly to a uniform magnetic field that increases its magnitude at a constant rate from 2.0T to 6.0T in 2.0s. if the coil has a total resistance of 0.40 ohms, what is the magnitude of the induced current

500 mA

38. what is the self-inductance in a coil, which experiences a 3.0 V induced emf, when the current is changing at a rate of 55 A/s

54 mH

27. a straight wire 40cm long moves with a velocity of 20 m/s in a direction perpendicular to its length through a uniform magnetic field of 1.5 T inclined at 30 degrees to the wire. it moves along a U-shape conductor. the induced emf is

6.0V

53. a circular loop of radius 0.10 m is rotating in a uniform magnetic field of 0.20T Find the magnetic flux through the loop when the plane of the loop and the magnetic field vector are perpendicular

6.3 x10^-3 Tm^2

49. what is the wavelength of light waves if their frequency is 5.0x10^14 Hz

600 nm

29. an ac power generator produces 25 A(rms) at 3600 V. the energy is transmitted through a long distance power line which has a total resistance of 100 ohms. what percentage of the power delivered by the generator is dissipated as heat in the long distance line if a step-up transformer is not used

69%

12. the distance between the earth and the sun is 1.49x10^11m. How much time, in minutes, does it take for sunlight to reach the earth

8.3 min

42. a circular loop of one turn and radius 5cm is positioned with its axis parallel to a magnetic field of 0.6T. suddenly the area of the loop collapses to zero in 0.5 ms. what emf was induced

9.4 V

56. a 150-W lamp is placed into a 120-V ac outlet. what is the resistance of the lamp

96 ohm

36. the electric field, E, in an electromagnetic wave is oriented in what direction with respect to its associated magnetic field, B?

E perpendicular to B

21. the principle or law which says that an induced emf in a circuit loop produces a current whose magnetic field opposes further change of magnetic flux, is credited to which one of the following scientists

Lenz

40. the units of magnetic flux are not:

T/(volt-m)

2. Smashing high-energy electrons into tungsten or some other metal produces

X-Rays

15. in which of the following situations is an electric current NOT produced

a loop of wire is stationary in a steady magnetic field

7. which one of the following will not generate electromagnetic waves or pulses

a stationary charge

17. which one of the following statements concerning transformers is false

a transformer can function with either an ac current or a steady dc current

3. In which of the following situations is an electric current NOT produced

a wire has been wrapped around a stationary magnet

35. which condition of motion must be met with regard to a charged particle if it is in the process of emitting electromagnetic radiation

accelerates

43. a wire moves across a magnetic field. the emf induced in the wire depends on

all of the above: the fields magnetic flux the length of wire the orientation of the wire relative to the magnetic field

51. a wire moves across a magnetic field. the emf produced in the wire depends on

all of the given answers

20. a bar magnet is falling through a loop of wire with constant velocity with the North Pole entering first. as the South Pole leaves the loop of wire the induced current will be as viewed from above

clockwise

19. a bar magnet is falling through a loop of wire with constant velocity with the North Pole entering first. as the North Pole enters the wire, the induces current will be, as viewed from above

counterclockwise

39. what fundamental fact underlies the operation of electric motors

current-carrying conductor placed perpendicular to a magnetic field will experience force

6. which one of the following statements concerning electromagnetic waves is false

electromagnetic waves are longitudinal waves

1. your remote will switch TV channels by sending out

infrared signals

45. doubling the number of loops of a wire in a coil produces what kind of change on the induced emf

it doubles it

18. the basic function of the electric transformer is which one of the following conversion processes

low alternating voltage to high alternating voltage or vice versa

22. the basic function of the electric generator is which one of the following conversion processes

mechanical energy to electrical

47. a flux of a 4x10^-5 Wb is maintained through a coil for 0.5s. what is the induced emf in this coil by this flux

no emf

33. the self-inductance of a solenoid increases under which of the following conditions?

number of coils is increased

16. which of the following is NOT true for electromagnetic waves

only a very restricted range of frequencies can exist

24. according to Lenz's law the direction of an induced current in a conductor will be that which tends to produce which of the following effects

oppose the effect which produces it

61. what do the letters 'rms' stand for

root mean square

48. a coil lies flat on a tabletop and external magnetic field points straight up. the magnetic field vanishes suddenly. as seen from above what is the induced emf

the induced current is counterclockwise

44. faraday's law of induction states that the emf induced in a loop of wire is proportional to

the time variation of the magnetic flux

52. a horizontal rod(oriented in the east-west direction) is moved northward at constant velocity through a magnetic field that points straight down. make a statement concerning the potential induced across the rod

the west end of the rod is at a higher potential than the east end

23. which statement below best pertains to the electromagnetic radiation

transmits both energy and momentum

34. glass panes are opaque to a certain type of radiation, which passes through quartz. what type of radiation is it

ultraviolet

9. which one of the following colors of visible light has the highest frequency

violet

4. A transformer can be used to increase the

voltage of ac electricity

8. which one of the following types of wave is intrinsically different from the other four

water waves