69 terms

Physics Exam

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
The voltage across the input terminals of a transformer is 110 V. The primary has 50 loops and the secondary has 25 loops. The voltage the transformer puts out is
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
The intensity of cosmic rays bombarding the Earth's surface is largest at the
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
9. If you use 10 J of work to push 2 coulombs of charge into an electric field, its voltage with respect to its starting position is
10. A step-up transformer decreases
11. Compared to a single lamp connected to a battery, two identical lamps connected in series to the same battery will carry
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
13. In a household electrical circuit, the wall outlets and room light switches are all connected in
14. Heat a copper wire and its electric resistance
15. A main difference between gravitational and electric forces is that electrical forces
repel or attract
16. When a 10-V battery is connected to a resistor, the current in the resistor is 2 A. What is the resistor's value?
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
20. Which pole of a compass needle points to a south pole of a magnet?
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
26. The electric field inside an uncharged metal ball is zero. If the ball is negatively charged, the electric field inside the ball is then
27. Electrons move in an electrical circuit
a. By interacting with an established electric field
28. A 2-C charge is placed in a location where the electric field is 10 N/C. How much electric force is exerted on the charge?
20 N
29. The unit of electric charge, the coulomb, is the charge on
a. A specific large number of electrons
30. When a 60-watt light bulb is connected to a 120-volt source the current in the light bulb is
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
34. When the distance between two charges is halved, the electrical force between the charges
a. Quadruples
35. To say that an object is electrically polarized is to say
a. Its charges have been rearranged
36. How much energy is stored by pushing 4 coulombs of charge into an electric field, where its voltage is 2 V greater compared to its starting position?
8 J
37. The direction of an electric field is the direction of the force that the field would exert on
a proton
38. A toaster with a resistance of 20 ohms is plugged into a 120 V outlet. What is the current in the toaster?
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
40. Stretch a copper wire so that it is thinner and the resistance between its ends
41. Which statement is correct
charge flows through a closed circuit
42. As a copper wire is cooled, its electric resistance
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
45. A coulomb of charge that passes through a 6-volt battery is given
6 J
46. A 6-V battery is connected to a resistor, and the current in the resistor is 3A. if the battery is replaced with a 12-V battery, what is the current in the resistor?
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
49. An electric heater is rated at 300 W when used in a 110-V circuit. The safety fuse in the circuit can handle 15 A of current. How many heaters can be safely operated in the circuit?
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
52. The voltage across the input terminals of a transformer is 110 V. The primary has 50 loops and the secondary has 100 loops. The voltage the transform puts out is
220 V
53. When the distance between two charges is tripled, the electrical force between the charges is
a. Nine times smaller
54. How much energy will a 9 V battery give to 3 coulombs of charge passing through it?
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
57. A charged balloon neatly illustrates that something can have a great amount of
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
59. When a single q is placed at one corner of a square, the electric field at the center of the square is F/q. If two other equal charges are placed at the adjacent corners of the square, the electric field at the center of the square due to these three equal charges is
60. Several paper clips dangle from the south pole of a magnet. The induced pole in the bottom of the uppermost paper clip is
south pole
61. The current through two identical light bulbs in series is 1/4 A. The voltage across both bulbs is 110 V. The resistance of a single bulb is
220 ohms
62. Charge carriers in a metal are electrons rather than protons because electrons are
loosely bound
63. The source of all magnetism is
a. Moving electric charge
64. As more lamps are put into a parallel circuit, the overall current in the power source
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
69. The electric power of a lamp that carries 2 A at 120 V is
240 watts