Physics Exam

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test 1

1. The third prong of an electrical power cord plug is for

Grounding the appliance

2. A device that rotates a coil in a magnetic field in order to output electrical energy is called

an electric generator

Electrons are made to flow in a wire when there is

A potential difference across its ends

55 v

The magnetic field lines of a current-carrying coil with many loops of wire

Become bunched together straight along the inside of the coil

If a steady magnetic field exerts a force on a moving charge, that force is directed

At right angles to the direction of the field and at right angles to the direction of the motion

poles

8. In class, when I brought a negatively charged rod close to the end of a 2x4 piece of wood, the wood began to swing toward the charged rod. The wood was attracted to the rod because

a. The charges in the wood were polarized

5V

Current

less current

12. To say that electric charge is conserved means that no case has ever been found where

a. Net charge has been created or destroyed

parallel

increases

repel or attract

5 ohms

17. When there is a change in the magnetic field in a closed loop of wire

a. Electromagnetic induction occurs
b. A current is created in the loop of wire
c. A voltage is induced in the wire

18. A positively charged rod is held near a metal can that rests on a dry wood table. If you touch the opposite side of the can momentarily with your finger the can is then

negatively charged

19. Normally a small party balloon charged to several thousand volts will have a relatively small amount of

charge and potential energy

north pole

21. The primary purpose of a lightning rod is to

a. Discharge the structure to which it is attached

22. When the distance between two charges is doubled, the electrical force between the charges

a. Is reduced by 1/4

23. A battery produces (direct current) and a generator produces (alternating current).

a. Direct current; alternating current

24. If a magnet is pushed into a coil, voltage is induced across the coil. If the same magnet is pushed into a coil twice as fast through half the number of loops,

a. The same voltage is induced

25. Two lamps, one with a thick filament and one with a thin filament, are connected in parallel to a battery. The voltage is greatest across the lamp with the

both are the same

zero

27. Electrons move in an electrical circuit

a. By interacting with an established electric field

20 N

29. The unit of electric charge, the coulomb, is the charge on

a. A specific large number of electrons

0.5 A

31. When a light switch is turned on in a dc circuit, the average speed of electrons in the lamp is

a. Less than 1 cm/s

32. Power is transmitted at high voltages because the corresponding current in the wires is

a. Low so that overheating of the wires is minimized

33. Surrounding every moving electron is

a. An electric field
b. A magnetic field

35. To say that an object is electrically polarized is to say

a. Its charges have been rearranged

8 J

a proton

6 A

39. Receiving an electric shock is much more dangerous when your skin is wet because

a. Wet skin reduces the body's resistance to electric current

increases

41. Which statement is correct

charge flows through a closed circuit

decreases

43. Most wall outlets in North American homes provide

a. Alternating current at 120 volts oscillating at 60 hertz

44. Which is more dangerous, touching a faulty 110-volt light fixture, or a van de graaff generator charged to 100,000 volts?

a. Touching the light fixture

6 J

6 A

47. An iron rod becomes magnetic when

a. The domains of aligned spinning electrons are aligned with each other in the same direction

48. The field surrounding every moving electron is

a. Always both electric and magnetic

a. More than 5

50. Electromagnetic induction occurs in a coil when there is a change in

a. Magnetic field intensity in the coil

51. A device that rotates a coil in a magnetic field in order to output electrical energy is called

a. An electric generator

220 V

53. When the distance between two charges is tripled, the electrical force between the charges is

a. Nine times smaller

27 J

55. In an ac circuit, the electric field

a. Changes magnitude and direction with time

56. An electron is shot from the right, toward a spot just between the ends of the horseshoe magnet. The electron

a. Is deflected into the plane of the page

voltage

58. An electroscope is charged positively as shown by foil leaves that stand apart. As a negative charge is brought close to the electroscope, the leaves

a. Fall closer together

F/q

south pole

220 ohms

loosely bound

63. The source of all magnetism is

a. Moving electric charge

increases

65. The headlights, radio, and defroster fan in an automobile are connected in

a. Parallel with a switch for each

66. An electromagnet made with a current-carrying coil can be made stronger by

a. Placing an iron core inside the coil
b. Increasing the number of loops in the coil

67. The principal advantage of ac power over dc power is that

a. Ac voltage can be transformed via conventional transformers

68. Voltage can be induced in a wire by

a. Changing the current in a nearby wire
b. Moving the wire near a magnet
c. Moving a magnet near the wire

240 watts

Example: