7. What is the current in a circuit if 15 coulombs of electric charge move past a given point in 3 seconds? (1) 5 A (3) 18 A (2) 12 A (4) 45 A

Transcription

1 1. Compared to the number of free electrons in a conductor, the number of free electrons in an insulator of the same volume is less the same greater 2. Most metals are good electrical conductors because their molecules are close together they have high melting points they have many intermolecular spaces through which the current can flow they have a large number of free electrons 3. If an insulator replaces a conductor in an electrical circuit, the flow of electrons in the circuit will be less the same greater 4. When the total resistance of a simple electrical circuit is decreased while keeping the voltage constant, the current in the electrical circuit will decrease remain the same increase 5. If the resistance of a circuit is doubled and the voltage remains unchanged, the current flowing in the circuit will be one-half as much one-fourth as much twice as much four times as much 6. As the value of a variable resistor is increased, while voltage is held constant, the current flow in the resistor will decrease remain the same increase 7. What is the current in a circuit if 15 coulombs of electric charge move past a given point in 3 seconds? 5 A 18 A 12 A 45 A 8. An ampere can be defined as one coulomb per second joule per coulomb ohm per volt Newton per coulomb 9. A wire carries a current of 2.0 amperes. How many electrons pass a given point in this wire in 1.0 second? The current traveling from the cathode to the screen in a television picture tube is ampere. How many electrons strike the screen in 5.0 seconds? A uniform copper wire has a resistance of 100 ohms. If the wire is cut into 10 equal lengths, the resistance of each piece will be 1 Ω 100 Ω 10 Ω 1,000 Ω 12. A piece of wire has a resistance of 8 ohms. A second piece of wire of the same composition, diameter, and temperature, but one-half as long as the first wire, has a resistance of 8 Ω 16 Ω 2 Ω 4 Ω 13. If the length of a copper wire is reduced by half, then the resistance of the wire will be halved quartered doubled quadrupled

2 14. A copper wire is part of a complete circuit through which current flows. Which graph best represents the relationship between the wire's length and its resistance? 15. A manufacturer recommends that the longer the extension cord used with an electric drill, the thicker (heavier gauge) the extension cord should be. This recommendation is made because the resistance of a wire varies directly with length and inversely with cross-sectional area inversely with length and directly with cross-sectional area directly with both length and cross-sectional area inversely with both length and cross-sectional area 16. A copper wire of length L and cross-sectional area A has resistance R. A second copper wire at the same temperature has a length of 2L and a cross-sectional area of 1 2A. What is the resistance of the second copper wire? R 2R 1 R 2 4R 17. To reduce the resistance of a metal conductor one should cool the conductor to a low temperature heat the conductor to a high temperature coat the conductor with an insulator wire the conductor in series with another resistor 18. As the temperature of a coil of copper wire increases, its electrical resistance decreases remains the same increases 19. When an incandescent light bulb is turned on, its thin wire filament heats up quickly. As the temperature of this wire filament increases, its electrical resistance decreases remains the same increases 20. The resistance of a copper wire is measured to be 4 ohms at 20ºC. If the wire is heated to 30ºC, the resistance of the wire will be zero ohms more than 4 ohms less than 4 ohms 4 ohms

3 21. The graph below shows the relationship between the potential difference across a metallic conductor and the electric current through the conductor at constant temperature T 1. Which graph best represents the relationship between potential difference and current for the same conductor maintained at a higher constant temperature, T 2? 22. The diagram below represents a lamp, a 10-volt battery, and a length of nichrome wire connected in series. 23. If the cross-sectional area of a fixed length of wire were decreased, the resistance of the wire would decrease remain the same increase 24. The resistance of a metallic wire conductor is inversely proportional to its tensile strength length cross-sectional area temperature As the temperature of the nichrome is decreased, the brightness of the lamp will decrease remain the same increase 25. A copper wire has a resistance of 200 ohms. A second copper wire with twice the cross-sectional area and the same length would have a resistance of 50Ω 200Ω 100Ω 400Ω

4 26. Which graph below best represents how the resistance (R) of a series of copper wires of uniform length and temperature varies with cross-sectional area (A)? 29. If both the cross-sectional area and the length of a metallic conductor were doubled, the resistance of the conductor would be halved unchanged doubled quadrupled 30. The graph below represents the relationship between potential difference and current for four different resistors. Which resistor has the greatest resistance? 27. The diagram below shows a circuit in which a copper wire connects points A and B. A C B D The electrical resistance between points A and B can be decreased by replacing the wire with a thicker copper wire of the same length replacing the wire with a longer copper wire of the same thickness increasing the temperature of the copper wire increasing the potential difference supplied by the battery 31. A student needs to increase the resistance in a circuit. All that is available for this task is a wide variety of wires of different lengths and thicknesses. To obtain the maximum resistance, the student should replace the wire with one that is shortest and thickest longest and thickest shortest and thinnest longest and thinnest 32. A 10.-meter length of wire with a cross-sectional area of square meter has a resistance of ohm at 20 Celsius. The wire is most likely made of silver aluminum copper tungsten 28. Which segment of copper wire has the highest resistance at room temperature? 1.0 m length, m 2 cross-sectional area 2.0 m length, m 2 cross-sectional area 1.0 m length, m 2 cross-sectional area 2.0 m length, m 2 cross-sectional area

5 33. The table below lists various characteristics of two metallic wires, A and B. If wire A has resistance R, then wire B has resistance R 2R R 2 4R 34. Which voltage would cause a current of 0.5 ampere in a circuit that has a resistance of 24 ohms? 6.0 V 24 V 12 V 48 V 35. If the potential difference across a 30.-ohm resistor is 10. volts, what is the current through the resistor? 0.25 A 3.0 A 0.33 A 0.50 A 36. A lamp has a current of 2.0 amperes at 6.0 volts. The resistance of the lamp must be 1.5 Ω 3.0 Ω 6.0 Ω 12 Ω 40. In a flashlight, a battery provides a total of 3.0 volts to a bulb. If the flashlight bulb has an operating resistance of 5.0 ohms, the current through the bulb is 0.30 A 1.5 A 0.60 A 1.7 A 41. A 50-watt lightbulb and a 100-watt lightbulb are each operated at 100 volts. Compared to the resistance of the 50- watt bulb, the resistance of the 100-watt bulb is half as great one-fourth as great twice as great four times as great 42. The diagram below represents a simple circuit consisting of a variable resistor, a battery, an ammeter, and a voltmeter. 37. A potential difference of 12 volts is applied across a circuit which has a 4.0-ohm resistance. What is the magnitude of the current in the circuit? 0.33 A 3.0 A 48 A 4.0 A 38. A series circuit has a total resistance of ohms and an applied potential difference of volts. The amount of charge passing any point in the circuit in 2.00 seconds is C C 2.00 C 4.00 C 39. A 20.-ohm resistor has 40. coulombs passing through it in 5.0 seconds. The potential difference across the resistor is 8.0 V 160 V 100 V 200 V What is the effect of increasing the resistance of the variable resistor from 1000 Þ to Þ? [Assume constant temperature.] The ammeter reading decreases. The ammeter reading increases. The voltmeter reading decreases. The voltmeter reading increases.

6 43. Which graph best represents the relationship between the current (I) and the potential difference (V) in a circuit in which resistance remains constant? 46. Which circuit segment has an equivalent resistance of 6 ohms? 47. The diagram below shows a circuit with three resistors. 44. The slope of the line on the graph at the right represents resistance of a material electric field intensity power dissipated in a resistor electrical energy 45. The graph below represents the relationship between the potential difference (V) across a resistor and the current (I) through the resistor. Through which entire interval does the resistor obey Ohm s law? AB CD BC AD What is the resistance of resistor R 3? 6.0 Ω 12 Ω 2.0 Ω 4.0 Ω 48. A student needs a 4-ohm resistor to complete a circuit. Only a large quantity of 1-ohm resistors are available. Which of the following should be done to complete the circuit? Connect four 1-ohm resistors in series. Connect four 1-ohm resistors in parallel. Connect two of the 1-ohm resistors in series and two in parallel. Connect only two 1-ohm resistors in parallel. 49. Which quantity must be the same for each component in any series circuit? voltage resistance power current 50. A 5-ohm and a 10-ohm resistor are connected in series. The current in the 5-ohm resistor is 2 amperes. The current in the 10-ohm resistor is 1 A 0.5 A 2 A 8 A

7 51. The diagram below represents a series circuit containing three resistors. 54. A 9.0-volt battery is connected to a 4.0-ohm resistor and a 5.0-ohm resistor as shown in the diagram below. What is the current through resistor R 2? 1.0 A 3.0 A 0.33 A 9.0 A 52. The diagram below represents a simple electric circuit. What is the current in the 5.0-ohm resistor? 1.0 A 1.8 A 2.3 A 4.0 A 55. The diagram below represents an electric circuit. How much charge passes through the resistor in 2.0 seconds? 6.0 C 8.0 C 2.0 C 4.0 C 53. A 30.-ohm resistor and a 60.-ohm resistor are connected in an electric circuit as shown below. If the voltage between A and B is 10 volts, the voltage between B and C is 5 V 15 V 10 V 20 V 56. Three resistors of 20. ohms, 30. ohms, and 60. ohms, respectively, are connected in series with a battery. A current of 2.0 amperes will flow through this circuit when the potential difference of the battery is 10. V 110 V 20. V 220 V 57. As more resistors are added in series across a battery, the potential drop across each resistor decreases remains the same increases Compared to the electric current through the 30.-ohm resistor, the electric current through the 60.-ohm resistor is smaller the same larger

8 58. The diagram below shows a circuit with two resistors. 61. In the circuit shown below, voltmeter V 2 reads 80. volts. Compared to the potential drop across the 8-ohm resistor, the potential drop across the 4-ohm resistor is the same one-half as great twice as great four times as great 59. What is the voltage of the power supply shown on the below? What is the reading of voltmeter V 1? 160 V 40. V 80. V 20. V 62. Compared to the potential drop across the 10 ohm resistor shown in the diagram, the potential drop across the 5 ohm resistor is the same one-half as great twice as great four times as great 63. What is the current in the circuit represented in the diagram below? 0.5 volt 15 volts 10 volts 50 volts 60. The diagram below shows three resistors, R 1, R 2, and R 3, connected to a 12-volt battery. 1 A 3 A 2 A 6 A 64. In the circuit shown below, how many coulombs of charge will pass through resistor R in 2.0 seconds? If voltmeter V 1 reads 3 volts and voltmeter V 2 reads 4 volts, what is the potential drop across resistor R 3? 12 V 0 V 5 V 4 V 36 C 3.0 C 6.0 C 4.0 C

9 65. The diagram below shows a circuit with two resistors. 68. A 6.0-ohm lamp requires 0.25 ampere of current to operate. In which circuit below would the lamp operate correctly when switch S is closed? What is the reading on ammeter A? 1.3 A 3.0 A 1.5 A 0.75 A 66. The diagram below represents an electric circuit consisting of a 12-volt battery, a 3.0-ohm resistor, R 1, and a variable resistor, R 2. At what value must the variable resistor be set to produce a current of 1.0 ampere through R 1? 6.0 Þ 3.0 Þ 9.0 Þ 12 Þ 67. In the circuit represented by the diagram below, what is the reading of voltmeter V? V 30. V 2.0 V 40. V In the circuit diagram above, what is the potential difference across the 3.0-ohm resistor? 1.0 V 3.0 V 2.0 V 1.5 V

10 70. In the circuit shown at the right, the potential difference across the 4.0-ohm resistor is 73. Which circuit segment below has the same total resistance as the circuit segment shown in the diagram to the right? 6.0 volts 3.0 volts 2.0 volts 12 volts 71. Two identical resistors connected in series have a combined resistance of 8 ohms. When connected in parallel, the resistance of the combination will be 8 Ω 16 Ω 2 Ω 4 Ω 72. Three resistances of 2 ohms, 4 ohms, and 6 ohms are connected in parallel. The equivalent resistance of the three resistors is less than 2 Ω between 4 Ω and 6 Ω between 2 Ω and 4 Ω greater than 6 Ω 74. Circuit A and circuit B are shown below. Compared to the total resistance of circuit A, the total resistance of circuit B is less the same greater

11 75. Which two of the resistor arrangements shown below have equal resistances? 77. Which diagram represents resistances connected in series? A and B C and D B and C D and A 76. The total resistance of several resistors connected in parallel is equal to the sum of the separate resistances equal to the largest resistance smaller than the smallest resistance greater than the largest resistance 78. As more resistors are added in parallel, the total resistance of a circuit decreases remains the same increases 79. The diagram below shows a resistor of 5 ohms and a resistor of 10 ohms connected in parallel in a circuit. What is the total resistance of the circuit? less than 5 ohms 15 ohms 5 ohms greater than 15 ohms

12 80. Resistors R 1 and R 2 have an equivalent resistance of 6 ohms when connected in the circuit shown below. The resistance of R 1 could be 1 Ω 8 Ω 5 Ω 4 Ω 81. A physics student is given three 12-ohm resistors with instructions to create the circuit that would have the lowest possible resistance. The correct circuit would be a series circuit with an equivalent resistance of 36 Þ? series circuit with an equivalent resistance of 4.0 Þ? parallel circuit with an equivalent resistance of 36 Þ? parallel circuit with an equivalent resistance of 4.0 Þ? 82. In which circuit would ammeter A show the greatest current? 83. Two identical resistors connected in series have an equivalent resistance of 4 ohms. The same two resistors, when connected in parallel, have an equivalent resistance of 1 Þ 8 Þ 2 Þ 4 Þ

13 84. Ammeters A 1, A 2 and A 3 are placed in a circuit as shown below. 87. What is the current in ammeter A in the diagram below? 1 A 3 A 1/3 A 9 A What is the reading on ammeter A 3? 1.0 A 3.0 A 2.0 A 5.0 A 85. In the diagram below of a parallel circuit, ammeter A measures the current supplied by the 110-volt source. 88. An electric circuit contains an operating heating element and a lit lamp. Which statement best explains why the lamp remains lit when the heating element is removed from the circuit? The lamp has less resistance than the heating element. The lamp has more resistance than the heating element. The lamp and the heating element were connected in series. The lamp and the heating element were connected in parallel. 89. In the circuit diagram shown below, ammeter A 1 reads 10. amperes. The current measured by ammeter A is 1.0 A 5.5 A 0.10 A 11 A 86. The diagram below represents currents in a segment of an electric circuit. What is the reading of ammeter A 2? 6.0 A 20. A 10. A 4.0 A 90. When three 30-ohm resistors are connected in parallel across a 9-volt source, the total current is 0.10 A 0.45 A 0.30 A 0.90 A What is the reading of ammeter A? 1 A 3 A 2 A 4 A 91. A 10-ohm and a 20-ohm resistor are connected in parallel to a constant voltage source. If the current through the 10- ohm resistor is 4 amperes, then the current through the 20- ohm resistor is 1 A 8 A 2 A 4 A

14 92. In the circuit diagram below, ammeter A measures the current supplied by the 10.-volt battery. The current measured by ammeter A is 0.13 A 0.50 A 2.0 A 4.0 A 93. In the circuit diagram shown below, what is the current through the 4.0-ohm resistor? 96. A student uses a voltmeter to measure the potential difference across a circuit resistor. To obtain a correct reading, the student must connect the voltmeter in parallel with the circuit resistor in series with the circuit resistor before connecting the other circuit components after connecting the other circuit components 97. Which circuit shows the correct use of meters? (A-ammeter, V-voltmeter) 1.0 ampere 3.0 amperes 0.33 ampere 48 amperes 94. As the number of resistors in a parallel circuit is increased, what happens to the equivalent resistance of the circuit and total current in the circuit? Both equivalent resistance and total current decrease. Both equivalent resistance and total current increase. Equivalent resistance decreases and total current increases. Equivalent resistance increases and total current decreases. 95. Which circuit shown below could be used to determine the total current and potential difference of a parallel circuit? 98. In the circuits represented below, the symbol for the ammeter is A and the symbol for the voltmeter is V. Which diagram represents the proper connections for determining the resistance of the circuit?

15 99. What quantities may be directly measured by the arrangement of meters shown in the diagram below? voltage drop across R 2 and current through R 2 current through R 1 and R 2 current through R 1 and voltage drop across R 2 the resistance of R l and R Two resistors are connected to a source of voltage as shown in the diagram below. At which position should an ammeter be placed to measure the current passing only through resistor R 1? Which circuit diagram shows voltmeter V and ammeter A correctly positioned to measure the total potential difference of the circuit and the current through each resistor?

16 102. In which circuit represented below are meters properly connected to measure the current through resistor R 1 and the potential difference across R 2? 106. If energy is used in an electric circuit at the rate of 20 joules per second, then the power supplied to the circuit is 5 watts 25 watts 20 watts 100 watts 107. Two resistors are connected in parallel to a 12-volt battery as shown in the diagram. If the current in resistor R is 3.0 amperes, the rate at which R consumes electrical energy is W 24 W 36 W 4.0 W 108. A lamp and an ammeter are connected to a source as shown A 120-volt toaster is rated at 600 watts. Under normal conditions, the current in the toaster is 0.20 A 10. A 5.0 A 25 A 104. Which combination of current and electromotive force would use energy at the greatest rate? 10 A at 110 V 3 A at 220 V 8 A at 110 V 5 A at 110 V 105. Three resistors of 10 ohms, 20 ohms, and 30 ohms are connected in series to a 120-volt source. The power developed is greatest in the 10 Ω greatest in the 20 Ω resistor greatest in the 30 Ω resistor the same in all three resistors What is the electrical energy expended in the lamp in 3.0 seconds? 50. J 50. W 150 J 150 W 109. To increase the brightness of a desk lamp, a student replaces a 60-watt light bulb with a 100-watt bulb. Compared to the 60-watt bulb, the 100-watt bulb has less resistance and draws more current less resistance and draws less current more resistance and draws more current more resistance and draws less current 110. If the potential drop across an operating 300.-watt floodlight is 120 volts, what is the current through the floodlight? 0.40 A 7.5 A 2.5 A 4.5 A

17 111. In which of the circuits represented below will the resistor consume the most electrical power? 117. The same potential difference is applied to two lamps, A and B. The resistance of lamp A is twice the resistance of lamp B. Compared to the power developed by lamp B, the power developed by lamp A is less the same greater 118. While operating at 120 volts, an electric toaster has a resistance of 15 ohms. The power used by the toaster is 8.0 W 960 W 120 W 1,800 W 112. An air conditioner is designed to operate at 110 volts and is rated at 2,400 watts. Is it possible to use the air conditioner in a circuit which has a 15-ampere circuit breaker (or fuse) on a 110-volt line? Yes, because the current needed is less than 15 amperes. No, because the voltage required is too high. Yes, because the voltage is lower than that needed. No, because the current needed is greater than 15 amperes As the potential difference across a given resistor is increased, the power expended in moving charge through the resistor decreases remains the same increases 119. As the resistance of a lamp operating at a constant voltage increases, the power dissipated by the lamp decreases remains the same increases 120. As the resistance of a constant-voltage circuit is increased, the power developed in the circuit decreases remains the same increases 121. The heating element on an electric stove dissipates watts of power when connected to a 120-volt source. What is the electrical resistance of this heating element? Ω 3.3 Ω 0.60 Ω 36 Ω 122. The potential difference applied to a circuit element remains constant as the resistance of the element is varied. Which graph best represents the relationship between power (P) and resistance (R) of this element? 114. One watt is equivalent to one N m J s N/m J/s 115. A light bulb is in series with a rheostat variable resistor and a fixed voltage is applied across the total circuit. As the resistance of the rheostat decreases, the brightness of the bulb decreases remains the same increases 116. The potential difference across a 100.-ohm resistor is 4.0 volts. What is the power dissipated in the resistor? 0.16 W W 25 W 4.0 W

18 123. Identical resistors (R) are connected across the same 12-volt battery. Which circuit uses the greatest power? 127. How long must a 100-watt light bulb be used in order to dissipate 1,000 joules of electrical energy? 10 s 1,000 s 100 s 100,000 s 128. What is the current in a 1,200-watt heater operating on 120 volts? 0.10 A 10. A 5.0 A 20. A If the potential difference applied to a fixed resistance is doubled, the power dissipated by that resistance remains the same halves doubles quadruples 125. Assuming total conversion of electrical energy to heat energy, how many joules of heat energy are produced by a 20-watt heating unit in 5 seconds? 100 J 24 J 25 J 4 J 126. A series circuit contains a 4W and a 2W resistor connected to a 110-volt source. Compared to the energy dissipated in the 2W resistor, the energy dissipated in the 4W resistor during the same time is one-half as great twice as great the same four times as great The circuit represented in the diagram above is a series circuit. The electrical energy expended in resistor R in 2.0 seconds is 20. J 80. J 40. J 120 J 130. If the power developed in an electric circuit is doubled, the energy used in one second is halved quartered doubled quadrupled 131. An electric iron draws a current of 5 amperes and has a resistance of 20 ohms. The amount of energy used by the iron in 40 seconds is 100 J 4,000 J 500 J 20,000 J 132. A clothes dryer connected to a 240-volt line draws 30. amperes of current for 20. minutes. Approximately how much electrical energy is consumed by the dryer? J J J J 133. An electric dryer consumes 6.0 x 10 6 joules of energy when operating at 220 volts for 30. minutes. During operation, the dryer draws a current of approximately 10. A 20. A 15 A 25 A

19 134. How long will it take the immersion heater shown in the diagram below to deliver 1000 joules of heat to the water? 137. A 4.50-volt personal stereo uses 1950 joules of electrical energy in one hour. What is the electrical resistance of the personal stereo? 433 Ohms 37.4 Ohms 96.3 Ohms Ohms 138. How much work is done in moving 6 electrons through a potential difference of 2.0 volts? 6.0 ev 3.0 ev 2.0 ev 12 ev 0.2 sec 20 sec 2 sec 200 sec 135. How much time is required for an operating 100-watt light bulb to dissipate 10 joules of electrical energy? 1 s 10 s 0.1 s 1000 s 136. An operating electric heater draws a current of 10. amperes and has a resistance of 12 ohms. How much energy does the heater use in 60. seconds? 120 J 7200 J 1200 J 72,000 J 139. An elementary charge is accelerated by a potential difference of 9.0 volts. The total energy acquired by the charge is 9.0 ev 3.0 ev 12 ev 27 ev 140. An alpha particle with a charge of +2 elementary charges is accelerated in a vacuum through a potential difference of 10,000. volts. what is the energy acquired by the particle? ev 20,000. ev 2.0 ev 40,000. ev 141. An alpha particle with a charge of +2 elementary charges is accelerated by a potential difference of volts. The energy acquired by the particle is ev ev ev is ev

20 Answer Key Misc. User-Made Questions [Aug 10, 2009]

21 Answer Key Misc. User-Made Questions [Aug 10, 2009]

22 Answer Key Misc. User-Made Questions [Aug 10, 2009]