Halliday, Resnick, and Walker, Fundamentals of Physics 10e Question Answers

Chapter 27 Answers

1 (a) equal; (b) more 2 (a) no; (b) yes; (c) all tie 3 parallel, R2, R1, series 4 (a) b and d tie, then a tie of a, c, and e; (b) b, d, then a tie of a, c, and e; (c) positive x direction 5 (a) series; (b) parallel; (c) parallel 6 2.0 A 7 (a) less; (b) less; (c) more 8 (a) 3R; (b) R/3; (c) same 9 (a) parallel; (b) series 10 60 C

11 (a) same; (b) same; (c) less; (d) more 12 1, c; 2, a; 3, d; 4, b 13 (a) all tie; (b) 1, 3, 2

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Halliday/Resnick/Walker Fundamentals of Physics

Classroom Response System Questions

Chapter 27 Circuits

Reading Quiz Questions

27.2.1. Which one of the following statements concerning emf is true? 27.2.1. Which one of the following statements concerning emf is true? a) Emf is the work done in moving the current from one terminal to the a) Emf is the work done in moving the current from one terminal to the other of an emf device. other of an emf device. b) Emf is the work done in moving a single charge from one terminal to the b) Emf is the work done in moving a single charge from one terminal to the other of an emf device. other of an emf device. c) Emf is the force exerted on a single charge to move it from one terminal c) Emf is the force exerted on a single charge to move it from one terminal to the other of an emf device. to the other of an emf device. d) Emf is the total charge moving from one terminal to the other of an emf d) Emf is the total charge moving from one terminal to the other of an emf device. device. e) Emf is the electromagnetic force that is exerted between the terminals of e) Emf is the electromagnetic force that is exerted between the terminals of an emf device. an emf device.

27.3.1. What is the primary difference between an ideal emf device and a 27.3.1. What is the primary difference between an ideal emf device and a real emf device? real emf device? a) The electric potential of a real emf device is limited. a) The electric potential of a real emf device is limited. b) The resistance of a real emf device is finite, but the resistance of an ideal b) The resistance of a real emf device is finite, but the resistance of an ideal emf device is assumed to be infinite. emf device is assumed to be infinite. c) A real emf device can carry an electric current, but an ideal emf device c) A real emf device can carry an electric current, but an ideal emf device does not. does not. d) A real emf device has an internal resistance, but an ideal emf device does d) A real emf device has an internal resistance, but an ideal emf device does not. not. e) A real emf device has a potential difference across its terminals, but an e) A real emf device has a potential difference across its terminals, but an ideal emf device does not. ideal emf device does not.

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27.3.2. Which one of the following units is the correct SI unit for the 27.3.2. Which one of the following units is the correct SI unit for the electromotive force (emf)? electromotive force (emf)? a) newtons (N) a) newtons (N) b) coulombs (C) b) coulombs (C) c) joules (J). c) joules (J). d) amperes (A) d) amperes (A) e) volts (V) e) volts (V)

27.3.3. The positive terminal of a battery in a minivan has an electric 27.3.3. The positive terminal of a battery in a minivan has an electric potential that is a maximum of 12 V higher than the negative potential that is a maximum of 12 V higher than the negative terminal. Complete the following sentence: When wires are terminal. Complete the following sentence: When wires are connected to the battery from the various electrical circuits within connected to the battery from the various electrical circuits within the minivan, the potential difference between the two terminals is the minivan, the potential difference between the two terminals is a) equal to 12 V. a) equal to 12 V. b) less than 12 V. b) less than 12 V. c) greater than 12 V. c) greater than 12 V. d) equal to zero V. d) equal to zero V.

27.3.4. Which one of the following terms describes the resistance that 27.3.4. Which one of the following terms describes the resistance that a battery (or other emf device) has in a circuit? a battery (or other emf device) has in a circuit? a) super resistance a) super resistance b) critical resistance b) critical resistance c) internal resistance c) internal resistance d) terminal resistance d) terminal resistance e) electroresistance e) electroresistance

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27.4.1. In analyzing electric circuits containing a battery and at least 27.4.1. In analyzing electric circuits containing a battery and at least one resistor, what is the change in potential across a resistor as one one resistor, what is the change in potential across a resistor as one moves through it in the direction of the current? moves through it in the direction of the current? a) +i2R a) +i2R b) −i2R b) −i2R c) +iR c) +iR d) −iR d) −iR e) zero e) zero

27.4.2. In analyzing electric circuits containing an ideal emf device 27.4.2. In analyzing electric circuits containing an ideal emf device that has an emf  and at least one resistor, what is the change in that has an emf  and at least one resistor, what is the change in potential across the emf device as one moves through it in the potential across the emf device as one moves through it in the direction of the emf arrow? direction of the emf arrow? a) + a) + b) − b) − c) + / R c) + / R d) − / R d) − / R e) zero e) zero

27.4.3. Complete the following statement: Around any closed-circuit 27.4.3. Complete the following statement: Around any closed-circuit loop, the sum of the potential drops loop, the sum of the potential drops a) dramatically with the addition of each resistor. a) dramatically with the addition of each resistor. b) in each loop is the same. b) in each loop is the same. c) equals the sum of the potential rises. c) equals the sum of the potential rises. d) equals the emf of the battery. d) equals the emf of the battery. e) increases with the addition of each resistor. e) increases with the addition of each resistor.

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27.5.1. Which one of the following statements is true concerning 27.5.1. Which one of the following statements is true concerning resistors connected in series within an electric circuit? resistors connected in series within an electric circuit? a) The potential difference across each of the resistors is the same. a) The potential difference across each of the resistors is the same. b) The current through each of the resistors is the same. b) The current through each of the resistors is the same. c) The energy dissipated by each of the resistors is the same. c) The energy dissipated by each of the resistors is the same. d) The resistance of each of the resistors is the same. d) The resistance of each of the resistors is the same. e) The resistivity of each of the resistors is the same. e) The resistivity of each of the resistors is the same.

27.5.2. Two identical resistors are connected in series across the 27.5.2. Two identical resistors are connected in series across the terminals of a battery with a voltage V and a current i flows terminals of a battery with a voltage V and a current i flows through the circuit. If one of the resistors is removed from the through the circuit. If one of the resistors is removed from the circuit and the remaining one connected across the terminals of the circuit and the remaining one connected across the terminals of the battery, how much current would flow through the circuit? battery, how much current would flow through the circuit? a) 4i a) 4i b) 2i b) 2i c) i c) i d) i/2 d) i/2 e) i/4 e) i/4

27.5.3. One end of resistor A is connected to the positive terminal of a 27.5.3. One end of resistor A is connected to the positive terminal of a battery and the other end is connected to resistor B. The opposite battery and the other end is connected to resistor B. The opposite end of resistor B is connected to the negative terminal of the end of resistor B is connected to the negative terminal of the battery. If resistor A has resistance R and B has a resistance 2R, battery. If resistor A has resistance R and B has a resistance 2R, what is the equivalent resistance of this circuit? what is the equivalent resistance of this circuit? a) R a) R b) 3R/2 b) 3R/2 c) 2R c) 2R d) 2R/3 d) 2R/3 e) 3R e) 3R

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27.6.1. Which of the following occurs when part of an electric circuit 27.6.1. Which of the following occurs when part of an electric circuit is connected to ground? is connected to ground? a) The ground acts like a battery, so the current in the circuit a) The ground acts like a battery, so the current in the circuit increases. increases. b) Any current in the circuit flows to the ground. b) Any current in the circuit flows to the ground. c) The electric potential at the connection point is equal to zero volts. c) The electric potential at the connection point is equal to zero volts. d) The electric potential difference across the terminals of any d) The electric potential difference across the terminals of any batteries in the circuit is equal to zero volts. batteries in the circuit is equal to zero volts. e) The ground provides a source for more electrons to flow into the e) The ground provides a source for more electrons to flow into the circuit. circuit.

27.7.1. While analyzing the currents within a circuit containing multiple 27.7.1. While analyzing the currents within a circuit containing multiple components (such as batteries, resistors, etc.), which of the following components (such as batteries, resistors, etc.), which of the following statements concerning currents flowing into a single junction must be true? statements concerning currents flowing into a single junction must be true? a) The sum of the currents entering the junction must equal the total current a) The sum of the currents entering the junction must equal the total current through the battery. through the battery. b) The sum of the currents entering the junction must equal zero. b) The sum of the currents entering the junction must equal zero. c) The sum of the currents entering the junction must equal the sum of the c) The sum of the currents entering the junction must equal the sum of the currents exiting the junction. currents exiting the junction. d) The currents entering the junction must follow only one of the possible exit d) The currents entering the junction must follow only one of the possible exit paths. paths. e) The currents entering the junction may exit back along the path from which e) The currents entering the junction may exit back along the path from which they entered. they entered.

27.7.2. The fact that the sum of the currents entering any junction in an 27.7.2. The fact that the sum of the currents entering any junction in an electric circuit must be equal to the sum of the currents leaving the electric circuit must be equal to the sum of the currents leaving the junction is an expression of what principle? junction is an expression of what principle? a) conservation of energy a) conservation of energy b) Heisenberg uncertainty principle b) Heisenberg uncertainty principle c) conservation of momentum c) conservation of momentum d) Archimedes' Principle d) Archimedes' Principle e) conservation of charge e) conservation of charge

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27.7.3. Which one of the following statements is true concerning 27.7.3. Which one of the following statements is true concerning resistors connected in parallel within an electric circuit? resistors connected in parallel within an electric circuit? a) The potential difference across each of the resistors is the same. a) The potential difference across each of the resistors is the same. b) The current through each of the resistors is the same. b) The current through each of the resistors is the same. c) The energy dissipated by each of the resistors is the same. c) The energy dissipated by each of the resistors is the same. d) The resistance of each of the resistors is the same. d) The resistance of each of the resistors is the same. e) The resistivity of each of the resistors is the same. e) The resistivity of each of the resistors is the same.

27.7.4. Which of the following statements concerning resistors that are 27.7.4. Which of the following statements concerning resistors that are wired in parallel is true? wired in parallel is true? a) The current through each resistor is necessarily the same. a) The current through each resistor is necessarily the same. b) The equivalent resistance for the resistors in the circuit is the sum b) The equivalent resistance for the resistors in the circuit is the sum of the individual resistances. of the individual resistances. c) The voltage across each resistor is necessarily the same. c) The voltage across each resistor is necessarily the same. d) The equivalent resistance for the resistors in the circuit is the d) The equivalent resistance for the resistors in the circuit is the product of the individual resistances. product of the individual resistances. e) The equivalent resistance for the resistors in the circuit is the e) The equivalent resistance for the resistors in the circuit is the average of the individual resistances. average of the individual resistances.

27.7.5. Two resistors can be either connected to a battery in series or in 27.7.5. Two resistors can be either connected to a battery in series or in parallel. In which case, if either, is the equivalent resistance the parallel. In which case, if either, is the equivalent resistance the smallest? smallest? a) When the two resistors are wired in parallel, the equivalent resistance a) When the two resistors are wired in parallel, the equivalent resistance is less than if they are wired in series. is less than if they are wired in series. b) When the two resistors are wired in series, the equivalent resistance is b) When the two resistors are wired in series, the equivalent resistance is less than if they are wired in parallel. less than if they are wired in parallel. c) Both series and parallel wiring will result in the same equivalent c) Both series and parallel wiring will result in the same equivalent resistance. resistance. d) It is not possible to know which method of wiring will result in the d) It is not possible to know which method of wiring will result in the lowest equivalent resistance without knowing the values of the two lowest equivalent resistance without knowing the values of the two resistances. resistances.

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27.7.6. In analyzing circuits in which resistors are wired partially in series and 27.7.6. In analyzing circuits in which resistors are wired partially in series and partially in parallel, which one of the following statements describes the partially in parallel, which one of the following statements describes the preferred approach to take to determine the equivalent resistance in the circuit? preferred approach to take to determine the equivalent resistance in the circuit? a) Find the sum of all the resistors. This is the equivalent resistance for the circuit. a) Find the sum of all the resistors. This is the equivalent resistance for the circuit. b) Break the circuit into smaller parts and find an equivalent resistance for each part. b) Break the circuit into smaller parts and find an equivalent resistance for each part. Then continue this process until all of the parts are added together correctly Then continue this process until all of the parts are added together correctly either in series or parallel until a single equivalent resistance is found. either in series or parallel until a single equivalent resistance is found. c) All together all of the resistors in series, ignoring any wired in parallel as they do c) All together all of the resistors in series, ignoring any wired in parallel as they do not significantly add to the equivalent resistance of the circuit. The sum of the not significantly add to the equivalent resistance of the circuit. The sum of the resistors in series is the equivalent resistance. resistors in series is the equivalent resistance. d) All together all of the resistors in parallel, ignoring any wired in series as they do d) All together all of the resistors in parallel, ignoring any wired in series as they do not significantly add to the equivalent resistance of the circuit. The sum of the not significantly add to the equivalent resistance of the circuit. The sum of the resistors in parallel is the equivalent resistance. resistors in parallel is the equivalent resistance.

27.7.7. Which one of the following choices is not one of Kirchoff’s 27.7.7. Which one of the following choices is not one of Kirchoff’s rules? rules? a) junction rule a) junction rule b) emf rule b) emf rule c) loop rule c) loop rule d) slide rule d) slide rule e) resistance rule e) resistance rule

27.7.8. Complete the following statement: The sum of the magnitudes 27.7.8. Complete the following statement: The sum of the magnitudes of the currents directed into a junction of the currents directed into a junction a) equals the sum of the magnitudes of the currents directed out of the a) equals the sum of the magnitudes of the currents directed out of the junction. junction. b) is less than the total current directed out of the junction. b) is less than the total current directed out of the junction. c) equals the current that is directed along one of the lines out of the c) equals the current that is directed along one of the lines out of the junction. junction. d) is divided equally among the number of lines directed out of the d) is divided equally among the number of lines directed out of the junction. junction. e) is greater than the total current directed out of the junction. e) is greater than the total current directed out of the junction.

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27.8.1. Which of the following devices is placed into a circuit to 27.8.1. Which of the following devices is placed into a circuit to measure the current that passes through it? measure the current that passes through it? a) ammeter a) ammeter b) gaussmeter b) gaussmeter c) voltmeter c) voltmeter d) diffractometer d) diffractometer e) flowmeter e) flowmeter

27.8.2. Which one of the following statements is not a characteristic of 27.8.2. Which one of the following statements is not a characteristic of a voltmeter? a voltmeter? a) The voltmeter measures the voltage between two points in a circuit. a) The voltmeter measures the voltage between two points in a circuit. b) The voltmeter is designed to measure nearly the same voltage that b) The voltmeter is designed to measure nearly the same voltage that is present when the meter is not connected. is present when the meter is not connected. c) The voltmeter is not placed directly into a circuit. c) The voltmeter is not placed directly into a circuit. d) The voltmeter is designed to draw very little current from the d) The voltmeter is designed to draw very little current from the circuit being measured. circuit being measured. e) An ideal voltmeter has almost no resistance. e) An ideal voltmeter has almost no resistance.

27.9.1. When does a charging capacitor stop charging? 27.9.1. When does a charging capacitor stop charging? a) when the amount of charge on the two plates is equal a) when the amount of charge on the two plates is equal b) when the potential difference across the plates of the capacitor is b) when the potential difference across the plates of the capacitor is equal to zero volts equal to zero volts c) when the amount of charge on the two plates is infinitely large c) when the amount of charge on the two plates is infinitely large d) when the potential difference across the plates of the capacitor is d) when the potential difference across the plates of the capacitor is equal to the emf of the battery equal to the emf of the battery e) when all of the charge available in the circuit has been forced to e) when all of the charge available in the circuit has been forced to collect on the plates of the capacitor collect on the plates of the capacitor

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27.9.2. What effect, if any, does increasing the resistance in an RC circuit have 27.9.2. What effect, if any, does increasing the resistance in an RC circuit have on the charging of the capacitor? on the charging of the capacitor? a) The resistance has no effect on the charging of the capacitor, which is a) The resistance has no effect on the charging of the capacitor, which is determined by the emf of the battery and the capacitance of the capacitor. determined by the emf of the battery and the capacitance of the capacitor. b) Increasing the resistance causes the charging time to increase since the rate at b) Increasing the resistance causes the charging time to increase since the rate at which charges are moving to the capacitor increases. which charges are moving to the capacitor increases. c) The charging time will decrease as the resistance is increased because the c) The charging time will decrease as the resistance is increased because the rate at which charges are moving to the capacitor decreases. rate at which charges are moving to the capacitor decreases. d) Increasing the resistance increases the charging time since the emf of the d) Increasing the resistance increases the charging time since the emf of the battery will be reduced. battery will be reduced. e) Increasing the resistance decreases the charging time since the emf of the e) Increasing the resistance decreases the charging time since the emf of the battery will be reduced. battery will be reduced.

27.9.3. What effect, if any, does increasing the capacitance in an RC circuit have 27.9.3. What effect, if any, does increasing the capacitance in an RC circuit have on the charging of the capacitor? on the charging of the capacitor? a) The capacitance has no effect on the charging of the capacitor, which is a) The capacitance has no effect on the charging of the capacitor, which is determined by the emf of the battery and the circuit resistance. determined by the emf of the battery and the circuit resistance. b) Increasing the capacitance causes the charging time to increase since the rate b) Increasing the capacitance causes the charging time to increase since the rate at which charges are moving to the capacitor increases. at which charges are moving to the capacitor increases. c) The charging time will decrease as the capacitance is increased because the c) The charging time will decrease as the capacitance is increased because the rate at which charges are moving to the capacitor decreases. rate at which charges are moving to the capacitor decreases. d) Increasing the capacitance increases the charging time since the capacitor can d) Increasing the capacitance increases the charging time since the capacitor can hold more charge. hold more charge. e) Increasing the capacitance decreases the charging time since the emf of the e) Increasing the capacitance decreases the charging time since the emf of the battery will be reduced. battery will be reduced.

27.9.4. Which of the following quantities is equal to the time constant 27.9.4. Which of the following quantities is equal to the time constant for a charging capacitor? for a charging capacitor? a) the time it takes a capacitor to reach 33 % of its maximum charge a) the time it takes a capacitor to reach 33 % of its maximum charge b) the time it takes a capacitor to reach 50 % of its maximum charge b) the time it takes a capacitor to reach 50 % of its maximum charge c) the time it takes a capacitor to reach 66 % of its maximum charge c) the time it takes a capacitor to reach 66 % of its maximum charge d) the time it takes a capacitor to reach 75 % of its maximum charge d) the time it takes a capacitor to reach 75 % of its maximum charge e) the time it takes a capacitor to reach its maximum charge e) the time it takes a capacitor to reach its maximum charge

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27.9.5. Consider each of the graphs shown. Which of these graphs 27.9.5. Consider each of the graphs shown. Which of these graphs represents the charge on a capacitor as it is being charged in a represents the charge on a capacitor as it is being charged in a circuit containing a resistor and a capacitor in series shortly after circuit containing a resistor and a capacitor in series shortly after they are connected to a battery? they are connected to a battery? a) A a) A b) B b) B c) C c) C d) D d) D e) E e) E

27.9.6. A circuit contains a capacitor with a capacitance C and a 27.9.6. A circuit contains a capacitor with a capacitance C and a resistor with a resistance R connected in series with a battery. resistor with a resistance R connected in series with a battery. Which one of the following mathematical expressions correctly Which one of the following mathematical expressions correctly represents the time constant for this circuit? represents the time constant for this circuit? a)  = 1 RC2 a) 2 R b)  = b) C c)  = RC c)

 = 1 RC d) 2 d) C e)  = e) R

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Halliday/Resnick/Walker Fundamentals of Physics

Classroom Response System Questions

Chapter 27 Circuits

Interactive Lecture Questions

27.3.1. In physics lab, two students measured the potential difference 27.3.1. In physics lab, two students measured the potential difference between the terminals of a battery and the current in a circuit connected between the terminals of a battery and the current in a circuit connected to the battery. The students then made a graph of the two parameters as to the battery. The students then made a graph of the two parameters as shown. They then drew a best fit line through the data. From their shown. They then drew a best fit line through the data. From their results, determine the approximate internal resistance of the battery. results, determine the approximate internal resistance of the battery. a) 0.002  a) 0.002  b) 0.08  b) 0.08  c) 0.1  c) 0.1  d) 0.3  d) 0.3  e) 0.6  e) 0.6 

27.3.2. A non-ideal battery has a 6.0-V emf and an internal resistance 27.3.2. A non-ideal battery has a 6.0-V emf and an internal resistance of 0.6 . Determine the terminal voltage when the current drawn of 0.6 . Determine the terminal voltage when the current drawn from the battery is 1.0 A. from the battery is 1.0 A. a) 5.0 V a) 5.0 V b) 6.0 V b) 6.0 V c) 5.4 V c) 5.4 V d) 6.6 V d) 6.6 V e) 5.8 V e) 5.8 V

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27.4.1. Consider a circuit that contains an ideal battery and a resistor to form 27.4.1. Consider a circuit that contains an ideal battery and a resistor to form a complete circuit. Which one of the following statements concerning a complete circuit. Which one of the following statements concerning the work done by the battery is true? the work done by the battery is true? a) No work is done by the battery in such a circuit. a) No work is done by the battery in such a circuit. b) The work done is equal to the thermal energy dissipated by the resistor. b) The work done is equal to the thermal energy dissipated by the resistor. c) The work done is equal to the work needed to move a single charge from c) The work done is equal to the work needed to move a single charge from one side of the battery to the other. one side of the battery to the other. d) The work done is equal to the emf of the battery. d) The work done is equal to the emf of the battery. e) The work done is equal to the product of the current flowing through the e) The work done is equal to the product of the current flowing through the circuit and the resistor. circuit and the resistor.

27.5.1. Two 20- resistors are connected in series. A potential 27.5.1. Two 20- resistors are connected in series. A potential difference of 9 V is then applied across the resistors. What is the difference of 9 V is then applied across the resistors. What is the resulting current through the resistors? resulting current through the resistors? a) 0.23 A a) 0.23 A b) 0.45 A b) 0.45 A c) 0.90 A c) 0.90 A d) 2.2 A d) 2.2 A e) 4.4 A e) 4.4 A

27.5.2. Consider the circuit shown in the drawing. Two identical light bulbs, labeled 27.5.2. Consider the circuit shown in the drawing. Two identical light bulbs, labeled A and B, are connected in series with a battery and are illuminated equally. A and B, are connected in series with a battery and are illuminated equally. There is a switch in the circuit that is initially open. Which one of the following There is a switch in the circuit that is initially open. Which one of the following statements concerning the two bulbs is true after the switch is closed? statements concerning the two bulbs is true after the switch is closed? a) Bulbs A and B will be off. a) Bulbs A and B will be off. b) Bulbs A and B will be equally b) Bulbs A and B will be equally illuminated. illuminated. c) Bulb A will be brighter and bulb B c) Bulb A will be brighter and bulb B will be off. will be off. d) Bulb A will be off and bulb B will be d) Bulb A will be off and bulb B will be brighter. brighter. e) Both bulbs will be dimmer than before the switch was closed. e) Both bulbs will be dimmer than before the switch was closed.

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27.5.3. Consider the three resistors and the battery in the circuit 27.5.3. Consider the three resistors and the battery in the circuit shown. Which resistors, if any, are connected in series? shown. Which resistors, if any, are connected in series? a) R1 and R2 a) R1 and R2 b) R1 and R3 b) R1 and R3 c) R2 and R3 c) R2 and R3 d) R1 and R2 and R3 d) R1 and R2 and R3 e) No resistors are connected in series. e) No resistors are connected in series.

27.5.4. Consider the circuit shown. If the ideal emf in the circuit is 24 27.5.4. Consider the circuit shown. If the ideal emf in the circuit is 24 V and the three resistances are R1 = 2.5 , R2 = 4.0 , and R3 = V and the three resistances are R1 = 2.5 , R2 = 4.0 , and R3 = 6.0 , determine the current in the 4.0  resistor. 6.0 , determine the current in the 4.0  resistor. a) 1.2 A a) 1.2 A b) 1.9 A b) 1.9 A c) 4.0 A c) 4.0 A d) 6.0 A d) 6.0 A e) 6.5 A e) 6.5 A

27.7.1 Two 20- resistors are connected in parallel. A potential 27.7.1 Two 20- resistors are connected in parallel. A potential difference of 9 V is then applied across both resistors. What is the difference of 9 V is then applied across both resistors. What is the resulting total current through the two resistors? resulting total current through the two resistors? a) 0.23 A a) 0.23 A b) 0.45 A b) 0.45 A c) 0.90 A c) 0.90 A d) 2.2 A d) 2.2 A e) 4.4 A e) 4.4 A

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27.7.2. Consider the three resistors and the battery in the circuit 27.7.2. Consider the three resistors and the battery in the circuit shown. Which resistors, if any, are connected in parallel? shown. Which resistors, if any, are connected in parallel? a) R1 and R2 a) R1 and R2 b) R1 and R3 b) R1 and R3 c) R2 and R3 c) R2 and R3 d) R1 and R2 and R3 d) R1 and R2 and R3 e) No resistors are connected in parallel. e) No resistors are connected in parallel.

27.7.3. Consider the circuits shown in parts A and B in the picture. In part A, a light 27.7.3. Consider the circuits shown in parts A and B in the picture. In part A, a light bulb is plugged into a wall outlet that has a voltage of 120 volts. A current i bulb is plugged into a wall outlet that has a voltage of 120 volts. A current i passes through the circuit and the bulb turns on. In part B, a second, identical passes through the circuit and the bulb turns on. In part B, a second, identical light bulb is connected in parallel in the circuit. How does the total current in light bulb is connected in parallel in the circuit. How does the total current in circuit B compare with that in circuit A? circuit B compare with that in circuit A? a) The current is the same, i, as in part A. a) The current is the same, i, as in part A. b) The current is twice as much, 2i, b) The current is twice as much, 2i, as in part A. as in part A. c) The current in part B is zero amperes. c) The current in part B is zero amperes. d) The current is one fourth as much, d) The current is one fourth as much, 0.25i, as in part A. 0.25i, as in part A. e) The current is one half as much, 0.5i, as in part A. e) The current is one half as much, 0.5i, as in part A.

27.7.4. Two light bulbs, one “50 W” bulb and one “100 W” bulb, are 27.7.4. Two light bulbs, one “50 W” bulb and one “100 W” bulb, are connected in parallel with a standard 120 volt ac electrical outlet. connected in parallel with a standard 120 volt ac electrical outlet. The brightness of a light bulb is directly related to the power it The brightness of a light bulb is directly related to the power it dissipates. Therefore, the 100 W bulb appears brighter. How does dissipates. Therefore, the 100 W bulb appears brighter. How does the brightness of the two bulbs compare when these same bulbs are the brightness of the two bulbs compare when these same bulbs are connected in series with the same outlet? connected in series with the same outlet? a) Both bulbs will be equally bright. a) Both bulbs will be equally bright. b) The “100 W” bulb will be brighter. b) The “100 W” bulb will be brighter. c) The “50 W” bulb will be brighter. c) The “50 W” bulb will be brighter.

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27.7.5. Consider the three identical light bulbs shown in the circuit. Bulbs B 27.7.5. Consider the three identical light bulbs shown in the circuit. Bulbs B and C are wired in series with each other and are wired in parallel with and C are wired in series with each other and are wired in parallel with bulb A. When the bulbs are connected to the battery as shown, how does bulb A. When the bulbs are connected to the battery as shown, how does the brightness of each bulb compare to the others? the brightness of each bulb compare to the others? a) Bulbs B and C are equally bright, a) Bulbs B and C are equally bright, but bulb A is less bright. but bulb A is less bright. b) Bulbs B and C are equally bright, b) Bulbs B and C are equally bright, but less bright than bulb A. but less bright than bulb A. c) All three bulbs are equally bright. c) All three bulbs are equally bright. d) Bulbs A and B are equally bright, but bulb C is less bright. d) Bulbs A and B are equally bright, but bulb C is less bright. e) Only bulb A is illuminated. e) Only bulb A is illuminated.

27.7.6. A circuit is formed using a battery, three identical resistors, and 27.7.6. A circuit is formed using a battery, three identical resistors, and connecting wires as shown. How does the current passing through connecting wires as shown. How does the current passing through

R3 compare with that passing through R1? R3 compare with that passing through R1?

a) I3 < I1 a) I3 < I1 b) I3 = I1 b) I3 = I1 c) I3 > I1 c) I3 > I1 d) This cannot be determined without knowing the amount of current d) This cannot be determined without knowing the amount of current

passing through R2. passing through R2.

27.7.7. What is the approximate equivalent resistance of the five 27.7.7. What is the approximate equivalent resistance of the five resistors shown in the circuit? resistors shown in the circuit? a) 21  a) 21  b) 7  b) 7  c) 11  c) 11  d) 14  d) 14  e) 19  e) 19 

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27.7.8. What is the current through the 4- resistor in this circuit? 27.7.8. What is the current through the 4- resistor in this circuit? a) 1.27 A a) 1.27 A b) 1.75 A b) 1.75 A c) 2.0 A c) 2.0 A d) 3.3 A d) 3.3 A e) 4.5 A e) 4.5 A

27.7.9. What is the current through the 1- resistor in this circuit? 27.7.9. What is the current through the 1- resistor in this circuit? a) 2.8 A a) 2.8 A b) 3.0 A b) 3.0 A c) 3.4 A c) 3.4 A d) 4.3 A d) 4.3 A e) 4.8 A e) 4.8 A

27.7.10. Which one of the following equations is not correct relative 27.7.10. Which one of the following equations is not correct relative to the other four equations determined by applying Kirchoff’s to the other four equations determined by applying Kirchoff’s Rules to the circuit shown? Rules to the circuit shown?

a) I2 = I1 + I4 a) I2 = I1 + I4 b) I2 = I3 + I5 b) I2 = I3 + I5 c) 6 V − (8 ) I1 − (5 ) I2 − (4 ) I3 = 0 c) 6 V − (8 ) I1 − (5 ) I2 − (4 ) I3 = 0 d) 6 V − (6 ) I4 − (5 ) I2 − (2 ) I5 = 0 d) 6 V − (6 ) I4 − (5 ) I2 − (2 ) I5 = 0 e) 6 V − (8 ) I1 − (6 ) I4 − 6 V − (2 ) I5 − (4 ) I3 = 0 e) 6 V − (8 ) I1 − (6 ) I4 − 6 V − (2 ) I5 − (4 ) I3 = 0

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27.7.11. Some light bulbs are connected in parallel to a 120 V source 27.7.11. Some light bulbs are connected in parallel to a 120 V source as shown in the figure. Each bulb dissipates an average power of as shown in the figure. Each bulb dissipates an average power of 60 W. The circuit has a fuse F that burns out when the current in 60 W. The circuit has a fuse F that burns out when the current in the circuit exceeds 9 A. Determine the largest number of bulbs, the circuit exceeds 9 A. Determine the largest number of bulbs, which can be used in this circuit without burning out the fuse. which can be used in this circuit without burning out the fuse. a) 9 a) 9 b) 17 b) 17 c) 25 c) 25 d) 34 d) 34 e) 36 e) 36

27.9.1. What effect, if any, does increasing the battery emf in an RC circuit 27.9.1. What effect, if any, does increasing the battery emf in an RC circuit have on the time to charge the capacitor? have on the time to charge the capacitor? a) The charging time will decrease because the rate of charge flowing to the a) The charging time will decrease because the rate of charge flowing to the plates will increase. plates will increase. b) The charging time will decrease because the rate of charge flowing to the b) The charging time will decrease because the rate of charge flowing to the plates will decrease. plates will decrease. c) The charging time will not change because the charging time does not c) The charging time will not change because the charging time does not depend on the battery emf. depend on the battery emf. d) The charging time will increase because the emf is increased. d) The charging time will increase because the emf is increased. e) The charging time will decrease because potential difference across the e) The charging time will decrease because potential difference across the plates will be larger. plates will be larger.

27.9.2. The resistance in an RC circuit is comprised of a 1.5-M 27.9.2. The resistance in an RC circuit is comprised of a 1.5-M resistor in parallel with a 2.0-M resistor. What is the time resistor in parallel with a 2.0-M resistor. What is the time constant for this circuit if the capacitance is 2.5 µF? constant for this circuit if the capacitance is 2.5 µF? a) 2.0 s a) 2.0 s b) 7.0 ms b) 7.0 ms c) 5.0 µs c) 5.0 µs d) 120 s d) 120 s e) 4000 s e) 4000 s

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27.9.3. In physics lab, Rebecca measured the voltage across an unknown 27.9.3. In physics lab, Rebecca measured the voltage across an unknown capacitor in an RC circuit, every ten seconds after a switch in the circuit capacitor in an RC circuit, every ten seconds after a switch in the circuit that allows the capacitor to discharge is closed. The capacitor was that allows the capacitor to discharge is closed. The capacitor was initially fully charged. Using the graph, estimate the time constant. initially fully charged. Using the graph, estimate the time constant. a) 7.5 s a) 7.5 s b) 15 s b) 15 s c) 30 s c) 30 s d) 45 s d) 45 s e) 60 s e) 60 s

27.9.4. An RC circuit contains a battery, a switch, a resistor, and a capacitor 27.9.4. An RC circuit contains a battery, a switch, a resistor, and a capacitor – all connected in series. Initially, the switch is open and the capacitor is – all connected in series. Initially, the switch is open and the capacitor is uncharged. Which one of the following statements correctly describes uncharged. Which one of the following statements correctly describes the current in the circuit during the time the capacitor is charging? the current in the circuit during the time the capacitor is charging? a) The current is increasing with increasing time. a) The current is increasing with increasing time. b) The current is constant with increasing time. b) The current is constant with increasing time. c) The current is decreasing with increasing time. c) The current is decreasing with increasing time. d) The current increases for the first half of the time until the capacitor is d) The current increases for the first half of the time until the capacitor is fully discharged, and then decreases during the second half of the time. fully discharged, and then decreases during the second half of the time. e) The current can either increase or decrease with increasing time e) The current can either increase or decrease with increasing time depending on the value of the time constant. depending on the value of the time constant.

27.9.5. An uncharged 5.0-µF capacitor and a resistor are connected in 27.9.5. An uncharged 5.0-µF capacitor and a resistor are connected in series to a 12-V battery and an open switch to form a simple RC series to a 12-V battery and an open switch to form a simple RC circuit. The switch is closed at t = 0 s. The time constant of the circuit. The switch is closed at t = 0 s. The time constant of the circuit is 4.0 s. What is the charge on either plate of the capacitor circuit is 4.0 s. What is the charge on either plate of the capacitor after one time constant has elapsed? after one time constant has elapsed? a) 7.4 × 10–5 C a) 7.4 × 10–5 C b) 5.5 × 10–5 C b) 5.5 × 10–5 C c) 1.2 × 10–5 C c) 1.2 × 10–5 C d) 3.8 × 10–5 C d) 3.8 × 10–5 C e) 2.2 × 10–5 C e) 2.2 × 10–5 C

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