chapter 23: electric current

C

11) The current through a 10-ohm resistor connected to a 120-V power supply is A) 1 A. B) 10 A. C) 12 A. D) 120 A. E) none of these

E

12) A 10-ohm resistor has a 5-A current in it. What is the voltage across the resistor? A) 5 V B) 10 V C) 15 V D) 20 V E) more than 20 V

B

13) When a 10-V battery is connected to a resistor, the current in the resistor is 2 A. What is the resistor's value? A) 2 ohms B) 5 ohms C) 10 ohms D) 20 ohms E) more than 20 ohms

A

17) In a common dc circuit, electrons move at speeds of A) a fraction of a centimeter per second. B) many centimeters per second. C) the speed of a sound wave. D) the speed of light. E) none of these

D

18) When a light switch is turned on in a dc circuit, the average speed of electrons in the lamp is A) the speed of sound waves in metal. B) the speed of light. C) 1000 cm/s. D) less than 1 cm/s. E) dependent on how quickly each electron bumps into the next electron.

B

2) An ampere is a unit of electrical A) pressure. B) current. C) resistance. D) all of these E) none of these

E

20) The electric power of a lamp that carries 2 A at 120 V is A) 1/6 watts. B) 2 watts. C) 60 watts. D) 20 watts. E) 240 watts.

B

21)When two lamps are connected in parallel to a battery, the electrical resistance that the battery senses is A)more than the resistance of either lamp. B)less than the resistance of either lamp. C)none of these

A

22) When two lamps are connected in series to a battery, the electrical resistance that the battery senses is A)more than the resistance of either lamp. B)less than the resistance of either lamp. C)none of these

C

23) On some early automobiles both headlights went out when one bulb burned out. The headlights must have been connected in A)parallel. B)perpendicular. C)series. D)haste.

A

24) Modern automobile headlights are connected in A) parallel. B) perpendicular. C) series. D) none of these

A

26) A 100-Watt lamp glows brighter than a 25-Watt lamp. The electrical resistance of the 100-Watt lamp must be A) less. B) greater. C) the same.

A

27) In an electric circuit, the safety fuse or circuit breaker is connected to the circuit in A) series. B) parallel. C) either series or parallel.

D

28) When a pair of 1-ohm resistors are connected in series, their combined resistance is A) 1 ohm, and when connected in parallel, 2 ohms. B) 2 ohms, and when in parallel, 1 ohm. C) 1/2 ohm, and when in parallel, 2 ohms. D) 2 ohms, and when in parallel, 1/2 ohm. E) none of these

B

29) A circuit breaker often serves the same purpose as a A) battery B) fuse. C) capacitor. D) All of the above choices are correct. E) None of the above choices are correct.

C

33) In a simple circuit containing a bulb, energy is given to the moving charges by A) the bulb. B) the wires. C) a generator. D) none of these

B

40) As more lamps are put into a series circuit, the overall current in the power source A) increases. B) decreases. C) stays the same.

A

41) As more lamps are put into a parallel circuit, the overall current in the power source A) increases. B) decreases. C) stays the same.

E

43) When we say an appliance "uses up electricity," we really are saying that A) current disappears. B) electric charges are dissipated. C) the main power supply voltage is lowered. D) electrons are taken out of the circuit and put somewhere else. E) electron kinetic energy is changed into heat

B

44) Compared to the resistance of two resistors connected in series, the same two resistors connected in parallel have A) more resistance. B) less resistance. C) the same resistance.

D

45) If you plug an electric toaster rated at 110 V into a 220-V outlet, the current in the toaster will be about A) half what it should be. B) the same as if it were plugged into 110 V. C) more than twice what it should be. D) twice what it should be.

B

46) When a 60-watt light bulb is connected to a 120-volt source the current in the light bulb is A)0.25 A. B)0.5 A. C) 2 A. D) 4 A. E)more than 4 A.

D

47) If 0.8 A of current flow through a light bulb connected to a 120 V outlet, the power consumed is A) 12 W. B) 15 W. C) 60 W. D) 96 W. E) 120 W.

B

48) The headlights, radio, and defroster fan in an automobile are connected in A) series with a switch for each. B) parallel with a switch for each. C) series without separate switches. D) parallel without separate switches.

A

49) A 4-ohm resistor is connected in parallel with a 6-ohm resistor. This combination produces an equivalent resistance of A) 2.4 ohms. B) 4 ohms. C) 5 ohms. D) 5.5 ohms. E) 10 ohms.

A

5) Which statement is correct? A) Charge flows in a closed circuit. B) Voltage flows through an open or a closed circuit. C) Resistance flows though an open circuit. D) Current is the primary cause of voltage.

C

50) The power dissipated in a 4-ohm resistor carrying 3 A is A) 7 W. B) 18 W. C) 36 W. D) 48 W. E) not enough information to say

A

51) 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 B)touching the generator C)Touching both are about equally dangerous.

A

52) A 60-W light bulb and a 100-W light bulb are each rated at 120 V. Which light bulb has a larger resistance? A) the 60-W bulb B) the 100-W bulb C) Both have the same resistance.

C

53) A 60-W light bulb and a 100-W light bulb are connected in series to a 120 V outlet. Which light bulb has more current in it? A) the 60-W bulb B) the 100-W bulb C) Both have the same current.

A

56) Compared to a single lamp connected to a battery, two lamps connected in parallel to the same battery will carry A) more current. B) less current. C) the same current.

D

57) 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)2 B)3 C)4 D)5 E)more than 5

C

58) A heater uses 20 A when used in a 110-V line. If electric power costs 10 cents per kilowatt hour, the cost of running the heater for 10 hours is A)$0.22. B)$0.55. C)$2.20. D)$5.50. E)none of these

C

59)The current through two identical light bulbs connected in series is 0.25 A. The voltage across both bulbs is 110 V. The resistance of a single light bulb is A) 22 ohms. B) 44 ohms. C) 220 ohms. D) 440 ohms. E) none of these

D

60) A power line with a resistance of 2 ohms has a current of 80 A in it. The power dissipated in the line is A) 40 W. B) 160 W. C) 320 W. D) 12,800 W. E) none of these

E

61) What is the resistance of a 120-W incandescent lamp connected to a 120-V power supply? A) 1 ohm B) 60 ohms C) 100 ohms D) 144 ohms E) none of these

D

62) Compared to the amount of electric current in the filament of a lamp, the amount of current in the connecting wire is A) definitely less. B) often less. C) actually more. D) the same. E) incredibly, all of these.

B

63) Connect a pair of lamps in series and you draw current from the connected battery. Connect the same lamps in parallel and you draw A) the same current. B) more current. C) less current. D) sometimes more, sometimes less.

C

64) Three resistors, 1-ohm, 2-ohm, and 3- ohm are connected in parallel. If they were connected in series instead their equivalent resistance would be A) 7 times as great. B) 9 times as great. C) 11 times as great. D) 13 times as great. E) None of the above choices are correct.

C

65) The ratio of the potential difference across a metallic conductor to the current in the conductor is known as A) potential drop. B) conductivity. C) resistance. D) electromagnetic force. E) None of the above choices are correct.

E

66) What condition must exist between two points in a conductor in order to maintain a flow of charge A) a steady magnetic field. B) a high resistance. C)a switch connected in series. D) All of the above choices are correct. E) None of the above choices are correct.

B

Compared to a single lamp connected to a battery, two identical lamps connected in series to the same battery will carry A) more current. B) less current. C) the same current.