Deck 18: Direct-Current Circuits Sources of EMF

Question 1

When a 29-Ω resistor is connected across a 16-V battery,a current of 470 mA flows.What is the resulting terminal voltage of the battery?

A) 34 V
B) 7.5 V
C) 13.6 V
D) ​61.7 V
E) ​0.6 V

Answer 1

13.6 V

Question 2

Three resistors,each with resistance R₁,are in series in a circuit.They are replaced by one equivalent resistor,R.Comparing this resistor to the first resistor of the initial circuit,which of the following is true?

A) The current through R equals the current through R₁.
B) The voltage across R equals the voltage across R₁.
C) The power given off by R equals the power given off by R₁.
D) R is less than R₁.

Answer 2

The current through R equals the current through R₁.

Question 3

When a 21-Ω resistor is connected across a 14-V battery,a current of 458 mA flows.What is the internal resistance of the battery?

A) 212 Ω
B) 9.6 Ω
C) 30.6 Ω
D) 0.7 Ω
E) ​1.1 Ω

Answer 3

9.6 Ω

Question 4

Three resistors connected in series have individual voltages labeled ΔV₁,ΔV₂ and ΔV₃,respectively.Which of the following expresses the value of the total voltage ΔV_T taken over the three resistors together?

A) ΔV_T = ΔV₁ + ΔV₂ + ΔV₃
B) ΔV_T = (1/ΔV₁ + 1/ΔV₂ + 1/ΔV₃)
C) ΔV_T = ΔV₁ = ΔV₂ = ΔV₃
D) ΔV_T = (1/ΔV₁ + 1/ΔV₂ + 1/ΔV₃)−¹

Question 5

Three resistors connected in series each carry currents labeled I₁,I₂ and I₃.Which of the following expresses the value of the total current I_T in the system made up of the three resistors in series?

A) I_T = I₁ + I₂ + I₃
B) I_T = (1/I₁ + 1/I₂ + 1/I₃)
C) I_T = I₁ = I₂ = I₃
D) I_T = (1/I₁ + 1/I₂ + 1/I₃)−¹

Question 6

Which voltage is not caused by a source of emf?

A) the voltage across a charged capacitor
B) the voltage across two copper-iron junctions at different temperatures
C) the voltage across the terminals of a dry cell battery
D) the voltage from an electric generator

Question 7

Three 5-Ω resistors are connected in parallel.What is their equivalent resistance?

A) 0.12 Ω
B) 2.5 Ω
C) 0.6 Ω
D) 1.7 Ω
E) ​5 Ω

Question 8

When a 19-Ω resistor is connected across a 5-V battery,a current of 489 mA flows.What is the power output delivered by the emf of the battery?

A) 95 W
B) 79.5 W
C) 4.5 W
D) 1.2 W
E) ​46.5 W

Question 9

Which resistor is in series with resistor R?

A) R₁
B) R₂
C) R₃
D) R₄

Question 10

The two ends of a 2.3-Ω resistor are connected to a 9.9-V battery.What is the total power delivered by the battery to the circuit?

A) 1.9 W
B) 42.6 W
C) 4.3 W
D) 52.4 W
E) ​225.4 W

Question 11

Four 7-Ω resistors are connected in series.What is their equivalent resistance?

A) 28 Ω
B) 7 Ω
C) 21 Ω
D) 1.8 Ω
E) ​11 Ω

Question 12

Resistors of values 5 Ω,17 Ω,and 24 Ω are connected in series across a battery with a small internal resistance.Which resistor dissipates the greatest power?

A) the 5-Ω resistor
B) the 17-Ω resistor
C) the 24-Ω resistor
D) The answer depends on the internal resistance of the battery.

Question 13

The basic function of an electromotive force in a circuit is to do which of the following?

A) Convert electrical energy into some other form.
B) Convert some other form of energy into electrical.
C) Both choices (a)and (b)are valid.
D) None of the above choices are valid.

Question 14

When a light bulb is turned on,its resistance increases until it reaches operating temperature.What happens to the current in the bulb as it is warming up?

A) It stays constant.
B) It increases.
C) It decreases.
D) It increases at first and then decreases.

Question 15

Three resistors,with values of 2,7 and 8 Ω,respectively,are connected in series.What is the overall resistance of this combination?

A) 1.3 Ω
B) 5.7 Ω
C) 7 Ω
D) 17 Ω
E) ​0.8 Ω

Question 16

Three resistors with values of R₁,R₂ and R₃,respectively,are connected in series.Which of the following expresses the total resistance,R_T,of the three resistors?

A) R_T = R₁ + R₂ + R₃
B) R_T = (1/R₁ + 1/R₂ + 1/R₃)
C) RT = R₁ = R₂ = R₃
D) R_T = (1/R₁ + 1/R₂ + 1/R₃)−¹

Question 17

Three 6-Ω resistors are connected in parallel to a 15-V battery.What is the current in any one of the resistors?

A) 21 A
B) 6.3 A
C) 2.5 A
D) 90 A
E) ​9 A

Question 18

If R₁ < R₂ < R₃,and if these resistors are connected in series in a circuit,which one dissipates the greatest power?

A) R₁
B) R₂
C) R₃
D) All are equal in power dissipation.

Question 19

The two ends of a 1.4-Ω resistor are connected to a 10.3-V battery.What is the current through the resistor?

A) 14.4 A
B) 0.1 A
C) 7.4 A
D) ​11.7 A
E) ​8.9 A

Question 20

The internal resistances of an ideal voltmeter and an ideal ammeter are respectively (ideal meaning the behavior of the system is not changed when using the meter):

A) zero and zero.
B) infinite and infinite.
C) zero and infinite.
D) infinite and zero.

Question 21

If ε = 9.0 V,what is the current in the 15-Ω resistor?

A) 0.20 A
B) 0.30 A
C) 0 10 A
D) 0.26 A

Question 22

Consider the circuit shown in the figure.What power is dissipated by the entire circuit?

A) 14 W
B) 28 W
C) 52 W
D) 112 W

Question 23

Two resistors of values 7 and 17 Ω are connected in parallel.This combination in turn is hooked in series with a 2-Ω resistor and a 20-V battery.What is the current in the 2-Ω resistor?

A) 5 A
B) 40 A
C) 0.8 A
D) 10 A
E) ​80 A

Question 24

Resistors of values 6.0Ω,4.0Ω,10.0Ω and 7.0Ω are combined as shown.What is the equivalent resistance for this combination?

A) 2.3 Ω
B) 3.0 Ω
C) 10.7 Ω
D) 27 Ω

Question 25

Three resistors connected in parallel have the individual voltages labeled ΔV₁,ΔV₂ and ΔV₃,respectively.Which of the following expresses the total voltage ΔV_T across the three resistors when connected in this manner?

A) ΔV_T = ΔV₁ + ΔV₂ + ΔV₃
B) ΔV_T = (1/ΔV₁ + 1/ΔV₂ + 1/ΔV₃)
C) ΔV_T = ΔV₁ = ΔV₂ = ΔV₃
D) ΔV_T = (1/ΔV₁ + 1/ΔV₂ + 1/ΔV₃)−¹

Question 26

Two resistors of values 6 and 11 Ω are connected in parallel.This combination in turn is hooked in series with a 4-Ω resistor and a 22-V battery.What is the current in the 4-Ω resistor?

A) 88 A
B) 2.8 A
C) 1 A
D) 5.5 A
E) ​173.8 A

Question 27

Which two resistors are in parallel with each other?

A) R and R₄
B) R₂ and R₃
C) R₂ and R₄
D) R and R₁

Question 28

Resistors of values 5 Ω,15 Ω,and 22 Ω are connected in parallel across a fresh battery.Which resistor dissipates the greatest power?

A) the 5-Ω resistor
B) the 15-Ω resistor
C) the 22-Ω resistor
D) All dissipate the same power when in parallel.

Question 29

Three resistors connected in parallel each carry currents labeled I₁,I₂ and I₃.Which of the following expresses the value of the total current I_T in the combined system?

A) I_T = I₁ + I₂ + I₃
B) I_T = (1/I₁ + 1/I₂ + 1/I₃)
C) I_T = I₁ = I₂ = I₃
D) I_T = (1/I₁ + 1/I₂ + 1/I₃)−¹

Question 30

If R₁ < R₂ < R₃,and if these resistors are connected in parallel in a circuit,which one has the highest current?

A) R₁
B) R₂
C) R₃
D) All have the same current.

Question 31

What is the equivalent resistance for these 3.00-Ω resistors?

A) 1.33 Ω
B) 2.25 Ω
C) 3.00 Ω
D) 7.50 Ω

Question 32

Three resistors,each with resistance R₁,are in parallel in a circuit.They are replaced by one equivalent resistor,R.Compare this resistor to the first resistor of the initial circuit.Which of the following statements is true?

A) The current through R equals the current through R₁.
B) The voltage across R equals the voltage across R₁.
C) The power given off by R equals the power given off by R₁.
D) R is greater than R₁.

Question 33

Three resistors with values R₁,R₂ and R₃,respectively,are connected in parallel.Which of the following expresses the total resistance,R_T,of the three resistors when connected in parallel?

A) R_T = R₁ + R₂ + R₃
B) R_T = (1/R₁ + 1/R₂ + 1/R₃)
C) RT = R₁ = R₂ = R₃
D) R_T = (1/R₁ + 1/R₂ + 1/R₃)−¹

Question 34

Three resistors connected in parallel have individual values of 4.0,6.0 and 10.0 Ω,respectively.If this combination is connected in series with a 12-V battery and a 2.0-Ω resistor,what is the current in the 10-Ω resistor?

A) 0.59 A
B) 1.0 A
C) 11 A
D) 16 A

Question 35

How much power is being dissipated by one of the 10-Ω resistors?

A) 24 W
B) 9.6 W
C) 16 W
D) 6.4 W

Question 36

Three resistors,with values of 4,6 and 15 Ω,respectively,are connected in parallel.What is the overall resistance of this combination?

A) 25 Ω
B) 2.1 Ω
C) 0.48 Ω
D) 8.3 Ω
E) ​7.1 Ω

Question 37

How much current is flowing in one of the 10-Ω resistors?

A) 0.8 A
B) 2.0 A
C) 1.6 A
D) 2.4 A

Question 38

Two resistors of values 8 and 17 Ω are connected in parallel.This combination in turn is hooked in series with a 5-Ω resistor.What is the overall resistance of this combination?

A) 2.6 Ω
B) 12.7 Ω
C) 10.4 Ω
D) 30 Ω
E) ​5.4 Ω

Question 39

If ε = 24 V,at what rate is thermal energy generated in the 20-Ω resistor?

A) 13 W
B) 3.2 W
C) 23 W
D) 39 W

Question 40

If ε = 20 V,at what rate is thermal energy being generated in the 20-Ω resistor?

A) 6.5 W
B) 1.6 W
C) 15 W
D) 26 W

Question 41

In a circuit,a current of 2 A is drawn from a battery.The current then divides and passes through two resistors in parallel.One of the resistors has a value of 66 Ω and the current through it is 0.5 A.What is the value of the other resistor?

A) 17 Ω
B) 22 Ω
C) 264 Ω
D) 13 Ω
E) ​198 Ω

Question 42

What is the potential difference between points a and b?

A) 6 V
B) 8 V
C) 12 V
D) 24 V

Question 43

What is the current flowing through the 4-Ω resistor?

A) 1 A
B) 2 A
C) 3 A
D) 6 A

Question 44

What is Kirchhoff's 1st equation for this junction?

A) I₁ = I₂ + I₃
B) I₂ = I₁+ I₂
C) I₃ = I₁ + I₂
D) I₁ + I₂ + I₃ = 0

Question 45

What is the current flowing through the 2-Ω resistor?

A) 2 A
B) 3 A
C) 4 A
D) 6 A

Question 46

In the circuit segment shown if I = 7 mA and Q = 50 µC,what is the potential difference,V_A - V_B?

A) −40 V
B) +40 V
C) +20 V
D) -20 V

Question 47

What is the current through the 8-Ω resistor?

A) 1.0 A
B) 0.50 A
C) 1.5 A
D) 2.0 A

Question 48

To find the equivalent resistance of the combination of resistors shown across the 28-V battery by the method of possibly repeated applications of combining resistors in series and /or combining resistors in parallel,the first step would be which of the following?

A) Combine the two 10 Ω in parallel since they can be done in your head.
B) Combine,in series,the two 3-Ω resistors and the 4-Ω resistor in the right-hand branch of the circuit.
C) Combine the seven resistors (two 5 Ω,three 3 Ω,one 2 Ω and one 4 Ω)in the outer loop of the circuit in series.
D) This problem cannot be done by combining series and parallel resistors.

Question 49

If I = 2.0 mA and the potential difference,V_A - V_B = +30 V in the circuit segment shown,determine the charge and polarity of the capacitor.

A) 1.5 mC,left plate is positive
B) 1.5 mC,right plate is positive
C) 0.50 mC,left plate is positive
D) 0.50 mC,right plate is positive

Question 50

A 10-V-emf battery is connected in series with the following: a 2-µF capacitor,a 2-Ω resistor,an ammeter,and a switch,initially open;a voltmeter is connected in parallel across the capacitor.At the instant the switch is closed,what are the current and capacitor voltage readings,respectively?

A) zero A,10 V
B) zero A,zero V
C) 5 A,zero V
D) 5 A,10 V

Question 51

If one doubles the emfs in a circuit and doubles the resistances in the circuit at the same time,what happens to the currents through the resistors? Assume there are only emfs and resistors in the circuit.

A) They stay the same.
B) They double.
C) They quadruple.
D) They halve.

Question 52

To find the equivalent resistance of the combination of resistors shown below by the method of possibly repeated applications of combining resistors in series and /or combining resistors in parallel,the first step would be which of the following?

A) Combine the 6.0 Ω and the 7.0 Ω in series.
B) Combine either the 4.0 Ω and the 10.0 Ω in parallel or the 7.0 Ω and the 10.0 Ω in parallel first,since either could be the first step with the other the second step.
C) Combine the 4.0 Ω and the 10.0 Ω in series.
D) Combine the 6.0 Ω,the 4.0 Ω,and the 10.0 Ω in series in a single step.

Question 53

A circuit contains a 6.0-V battery,a 4.0-Ω resistor,a 0.60-µF capacitor,an ammeter,and a switch all in series.What will be the current reading immediately after the switch is closed?

A) zero
B) 0.75 A
C) 1.5 A
D) 10 A

Question 54

What is the current through the 2-Ω resistor?

A) 1.0 A
B) 0.50 A
C) 1.5 A
D) 2.0 A

Question 55

A circuit contains a 6.0-V battery,a 4.0-Ω resistor,a 0.60-µF capacitor,an ammeter,and a switch in series.What will be the charge on the capacitor 10 min after the switch is closed?

A) zero
B) 0.10 μC
C) 3.6 μC
D) 2.4 μC

Question 56

A 1 000-V battery,a 3 000-Ω resistor,and a 0.50-µF capacitor are connected in series with a switch.The capacitor is initially uncharged.What is the value of the current the moment after the switch is closed?

A) 0.39 A
B) 0.33 A
C) 0.84 A
D) 2 000 A

Question 57

Five 1.5-volt AA batteries in series power a transistor radio.If the batteries hold a total charge of 200 C,how long will they last if the radio has a resistance of 180 Ω?

A) 8.3 h
B) 1.3 h
C) 0.7 h
D) 1 h
E) ​1.7 h

Question 58

If I₁ goes to the right through R₁,I₂ goes to the right through R₂,and I₃ goes to the right through R₃,what is the resulting equation resulting from applying Kirchhoff's junction rule at point b?

A) I₁ + I₂ + I₃ = 0
B) I₁ + I₂ - I₃ = 0
C) I₁ - I₂ + I₃ = 0
D) I₁ - I₂ - I₃ = 0

Question 59

A 10-V-emf battery is connected in series with the following: a 2-μF capacitor,a 2-Ω resistor,an ammeter,and a switch,initially open;a voltmeter is connected in parallel across the capacitor.After the switch has been closed for a relatively long period (several seconds,say),what are the current and capacitor voltage readings,respectively?

A) zero A,10 V
B) zero A,zero V
C) 5 A,zero V
D) 5 A,10 V

Question 60

If I₁ goes to the right through R₁,I₂ goes to the right through R₂,and I₃ goes to the right through R₃,what is the resulting equation resulting from applying Kirchhoff's loop rule for a clockwise loop around the perimeter of the circuit?

A) 8.0 V + I₁R₁ + I₃R₃ = 0
B) 8.0 V + I₁R₁ - I₃R₃ = 0
C) 8.0 V - I₁R₁ + I₃R₃ = 0
D) -8.0 V + I₁R₁ + I₃R₃ = 0

Question 61

A hair dryer draws 1,050 W,a curling iron draws 900 W,and an electric light fixture draws 450 W.If all three of these appliances are operating in parallel on a 120-V circuit,what is the total current drawn?

A) 6.7 A
B) 20 A
C) 1.9 A
D) 27.5 A
E) ​8.8 A

Question 62

Three resistors,each of different value,are used in a circuit with a power source supplying 12 volts.For which of the following resistor combinations is the total power supplied the greatest?

A) all three resistors in series
B) all three resistors in parallel
C) two of the resistors in parallel with the third resistor in series with the parallel pair
D) This cannot be found until it is known which resistor is in series with the parallel pair.

Question 63

A series RC circuit,which is made from a battery,a switch,a resistor,and a 5-μF capacitor,has a time constant of 8 ms.If an additional 7-μF is added in series to the 5-μF capacitor,what is the resulting time constant?

A) 11.2 ms
B) 4.7 ms
C) 0.5 ms
D) ​13.7 ms
E) ​This cannot be found without the value of the resistance being given.

Question 64

Household circuits are wired in ________.

A) series
B) parallel
C) both series and parallel
D) neither series nor parallel

Question 65

The following three appliances are connected to a 120-V house circuit: i)toaster,1,250 W,ii)coffee pot,600 W,and iii)microwave,800 W.If all were operated at the same time,what total current would they draw?

A) 2.2 A
B) 44.6 A
C) 7.4 A
D) 22.1 A
E) ​10.4 A

Question 66

A 1 000-V battery,a 3 000-Ω resistor and a 0.50-µF capacitor are connected in series with a switch.The time constant for such a circuit,designated by the Greek letter,τ,is defined as the time required to charge the capacitor to 63% of its capacity after the switch is closed.What is the value of τ for this circuit?

A) 6.0 × 10⁹ s
B) 1.7 × 10−¹⁰ s
C) 1.7 × 10−⁷ s
D) 1.5 × 10−³ s

Question 67

In an RC circuit using two capacitors in series with two resistors,which of the following combinations would give the greatest time constant?

A) both capacitors in series placed in series with both resistors in series
B) both capacitors in parallel placed in series with both resistors in parallel
C) both capacitors in series placed in series with both resistors in parallel
D) both capacitors in parallel placed in series with both resistors in series

Question 68

A certain capacitor is charged to 10 V and then,at t = 0,allowed to discharge through a certain resistor.There will be a certain time before the voltage across the capacitor reaches 5 V.This time can be decreased for this circuit by increasing:

A) the size of the capacitor.
B) the size of the resistor.
C) the size of the time constant.
D) None of the above.

Question 69

Using a resistor and two different value capacitors,which of the following combinations in an RC circuit would give the greatest time constant?

A) the resistor in series with both capacitors in series with each other
B) the resistor in series with both capacitors in parallel with each other
C) the resistor in series with the larger value capacitor
D) the resistor in series with the lower value capacitor

Question 70

Kirchhoff's rules are the junction rule and the loop rule.Which of the following statements is true?

A) Both rules are based on the conservation of charge.
B) Both rules are based on the conservation of energy.
C) The junction rule is based on the conservation of charge,and the loop rule is based on the conservation of energy.
D) The junction rule is based on the conservation of energy,and the loop rule is based on the conservation of charge.

Question 71

Using a capacitor and two different value resistors,which of the following combinations in an RC circuit would give the greatest time constant?

A) the capacitor in series with both resistors in series with each other
B) the capacitor in series with both resistors in parallel with each other
C) the capacitor in series with the higher value resistor
D) the capacitor in series with the lower value resistor

Question 72

A voltage source of 15 V is connected to a series RC circuit where R = 2 × 10⁶ Ω,and C = 1 µF.Find the amount of time required for the current in the circuit to decay to 6% of its original value.Hint: This is the same amount of time for the capacitor to reach 94% of its maximum charge.

A) 1.6 s
B) 3.6 s
C) 0.5 s
D) 5.6 s
E) ​11.2 s

Question 73

In applications where electrical shocks may be more likely,such as around water in kitchens and bathrooms,special outlets called GFI's are used.What does GFI stand for?

A) get free instantly
B) ground-fault interrupter
C) give fast interruption
D) gravity-free insulator

Question 74

A 1 000-V battery,a 3 000-Ω resistor,and a 0.50-μF capacitor are connected in series with a switch.The time constant for such a circuit,designated by the Greek letter,τ,is defined as the time that the capacitor takes to charge to 63% of its capacity after the switch is closed.What is the current in the circuit at a time interval of τ seconds after the switch has been closed?

A) 0.14 A
B) 0.21 A
C) 0.12 A
D) 0.32 A

Question 75

A series RC circuit has a time constant of 1.0 s.The battery has a voltage of 50 V and the maximum current just after closing the switch is 500 mA.The capacitor is initially uncharged.What is the charge on the capacitor 2.0 s after the switch is closed?

A) 0.43 C
B) 0 66 C
C) 0.86 C
D) 0.99 C

Question 76

What is the maximum number of 50-W light bulbs you can connect in parallel in a 100-V home circuit without tripping the 40-A circuit breaker?

A) 20
B) 39
C) 79
D) 59
E) ​58

Question 77

Household 120-V outlets are made to accept three-pronged plugs.One of the prongs attaches to the "live" wire at 120 V,and another attaches to the "neutral" wire that is connected to ground.What is the round third prong for?

A) It serves as a backup to the hot wire.
B) It lets the appliance run if the neutral wire breaks.
C) It connects the case of the appliance directly to ground for safety purposes.
D) Nothing electrical,it is for mechanical sturdiness.