Deck 17: Dc Circuits

Question 1

When there is electric current through an ionic liquid such as salty water,the moving charges are

A)only protons.
B)only electrons.
C)only negative ions.
D)only positive ions.
E)both positive and negative ions.

Answer 1

E

Question 2

If a quantity you calculated has units of A ∙ s,what is that quantity?

A)potential
B)resistivity
C)resistance
D)capacitance
E)charge

Answer 2

E

Question 3

A wire of resistivity ρ must be replaced in a circuit by a wire of the same material but four times as long.If,however,the total resistance is to remain as before,the diameter of the new wire must

A)be the same as the original diameter.
B)be one-half the original diameter.
C)be one-fourth the original diameter.
D)be two times the original diameter.
E)be four times the original diameter.

Answer 3

D

Question 4

The figure shows electrons passing through a resistor.The arrow shows the direction in which the electrons are moving.Which of the following statements are correct? (There could be more than one correct choice.)

A)The electrons are moving slower at point b than at point a.
B)The electric potential is higher at point b than at point a.
C)The electric potential is lower at point b than at point a.
D)The system electrons-metal is losing electric potential energy as the electrons move through the resistor from a to b.
E)The speed of the electrons at point b is the same as it is at point a.

Question 5

For the graph shown in the figure,what physical quantity does the slope of the graph represent for ohmic material?

A)power
B)resistivity
C)1/(resistivity)
D)resistance
E)1/(resistance)

Question 6

Copper wire #1 has a length L and a radius b.Copper wire #2 has a length 2L and a radius 2b.Which statement about the resistance across the ends of the wires is true?

A)The resistance of wire #1 is twice as high as that of wire #2.
B)The resistance of wire #1 is equal to that of wire #2.
C)The resistance of wire #1 is half that of wire #2.
D)The resistance of wire #1 is four times higher than that of wire #2.

Question 7

For the graph shown in the figure,what physical quantity does the slope of the graph represent for ohmic material?

A)current
B)resistivity
C)1/(current)
D)power
E)1/(resistivity)

Question 8

For the graph shown in the figure,what physical quantity does the slope of the graph represent for ohmic material?

A)current
B)resistivity
C)1/(current)
D)power
E)1/(resistivity)

Question 9

The length of a certain wire is kept same while its radius is doubled.What is the new resistance of this wire?

A)It is increased by a factor of 2.
B)It is increased by a factor of 4.
C)It is reduced by a factor of 2.
D)It is reduced by a factor of 4.
E)It is reduced by a factor of 8.

Question 10

The length of a certain wire is kept same while its radius is doubled.What is the new resistivity of this wire?

A)It is increased by a factor of 2.
B)It is increased by a factor of 4.
C)It is reduced by a factor of 2.
D)It is reduced by a factor of 4.
E)It does not change.

Question 11

When there is electric current through a metal wire,the moving charges are

A)only protons.
B)only electrons.
C)both protons and electrons.
D)positive metal ions.
E)negative metal ions.

Question 12

For the graph shown in the figure,what physical quantity does the slope of the graph represent for ohmic material?

A)power
B)resistivity
C)1/(resistivity)
D)resistance
E)1/(resistance)

Question 13

The length of a certain wire is doubled while its radius is kept constant.What is the new resistance of this wire?

A)It stays the same.
B)It is 2 times as large.
C)It is 3 times as large.
D)It is 4 times as large.
E)It is ½ as large.

Question 14

The figure shows a graph of the resistance of a wire as a function of its length.What physical quantities does the slope of this graph represent?

A)the cross-sectional area of the wire
B)the resistivity of the material of which the wire is made
C)the product of the resistivity and the cross-sectional area of the wire
D)the resistivity of the material divided by the cross-sectional area of the wire
E)the reciprocal of the resistivity of the material

Question 15

The length of a certain wire is doubled and at the same time its radius is also doubled.What is the new resistance of this wire?

A)It stays the same.
B)It is 2 times as large.
C)It is 4 times as large.
D)It is ½ as large.
E)It is ¼ as large.

Question 16

You are given a copper bar of dimensions 3 cm × 5 cm × 8 cm and asked to attach leads to it in order to make a resistor.If you want to achieve the smallest possible resistance,you should attach the leads to the opposite faces that measure

A)3 cm × 5 cm.
B)3 cm × 8 cm.
C)5 cm × 8 cm.
D)Any pair of faces produces the same resistance.

Question 17

You are given a copper bar of dimensions 3 cm × 5 cm × 8 cm and asked to attach leads to it in order to make a resistor.If you want to achieve the largest possible resistance,you should attach the leads to the opposite faces that measure

A)3 cm × 5 cm.
B)3 cm × 8 cm.
C)5 cm × 8 cm.
D)Any pair of faces produces the same resistance.

Question 18

The figure shows conventional current through a resistor.The arrow shows the direction of this conventional current.Which of the following statements are correct? (There could be more than one correct choice.)

A)The charges are moving slower at point b than at point a.
B)The electric potential is lower at point b than at point a.
C)The electric potential is higher at point b than at point a.
D)The current at point b is the same as the current at point a.
E)The electric potential at point b is the same as it is at point a.

Question 19

If a quantity you calculated has units of Ω ∙ m what is that quantity?

A)potential
B)resistivity
C)resistance
D)capacitance
E)charge

Question 20

If a quantity you calculated has units of ,what is that quantity?

A)potential
B)resistivity
C)resistance
D)capacitance
E)charge

Question 21

Consider two copper wires of equal cross-sectional area.One wire has 3 times the length of the other.How do the resistances of these two wires compare?

A)Both wires have the same resistance.
B)The longer wire has 1/3 the resistance of the shorter wire.
C)The longer wire has 3 times the resistance of the shorter wire.
D)The longer wire has 9 times times the resistance of the shorter wire.
E)The longer wire has 27 times times the resistance of the shorter wire.

Question 22

If a quantity you calculated has units of what is that quantity?

A)potential
B)resistivity
C)resistance
D)capacitance
E)current

Question 23

Consider two copper wires of equal length.One wire has twice the cross-sectional area of the other.How do the resistances of these two wires compare?

A)The thicker wire has twice the resistance of the thinner wire.
B)The thicker wire has eight times the resistance of the thinner wire.
C)The thicker wire has one-half the resistance of the thinner wire.
D)The thicker wire has four times the resistance of the thinner wire.
E)The thicker wire has one-fourth the resistance of the thinner wire.

Question 24

Which one of the following quantities is equivalent to 1 W?

A)1 V/A
B)1 Ω ∙ m
C)1 V ∙ A
D)1 V/Ω
E)1 A ∙ s

Question 25

During a period of high power demand,the voltage output of the power company is reduced by 5.0%.By what percentage is the power in a resistor decreased?

A)2.5%
B)5.0%
C)10%
D)15%
E)90%

Question 26

If the voltage across a circuit of constant resistance is doubled,the power dissipated by that circuit will

A)be four times as large.
B)be two times as large.
C)decrease to one-half the original power.
D)decrease to one-fourth the original power.

Question 27

If the resistance in a constant voltage circuit is doubled,the power dissipated by that circuit will

A)increase by a factor of two.
B)increase by a factor of four.
C)decrease to one-half its original value.
D)decrease to one-fourth its original value.

Question 28

The length of a certain wire is doubled and at the same time its radius is reduced by a factor of 2.What is the new resistance of this wire?

A)It is 2 times as large.
B)It is 4 times as large.
C)It is 6 times as large.
D)It it 8 times as large.
E)It is ½ as large.

Question 29

Which one of the following quantities is equivalent to 1 Ω?

A)1 J/s
B)1 W/A
C)1 V ∙ A
D)1 V/A
E)1 A ∙ s

Question 30

When the current through a resistor is increased by a factor of 4,the power dissipated by the resistor

A)decreases by a factor of 4.
B)decreases by a factor of 16.
C)increases by a factor of 16.
D)increases by a factor of 4.
E)increases by a factor of 2.

Question 31

Consider two copper wires with circular cross-sections and equal lengths.One wire has 3 times the diameter of the other.How do the resistances of these two wires compare?

A)The thicker wire has 1/3 the resistance of the thinner wire.
B)The thicker wire has 1/9 the resistance of the thinner wire.
C)The thicker wire has 3 times the resistance of the thinner wire.
D)The thicker wire has 9 times the resistance of the thinner wire.
E)The thicker wire has times the resistance of the thinner wire.

Question 32

If the length and diameter of a wire of circular cross section are both tripled,the resistance will be

A)unchanged.
B)tripled.
C)increased by a factor of 9.
D)1/3 of what it originally was.
E)1/9 of what it originally was.

Question 33

If we double the resistance in a circuit but keep the current through it constant,the power dissipated by that circuit will

A)be four times as great.
B)be two times as great.
C)be one-half as great.
D)be one-fourth as great.

Question 34

If the current through a circuit of constant resistance is doubled,the power dissipated by that circuit will

A)quadruple in magnitude.
B)double in magnitude.
C)decrease to one-half of what it was.
D)decrease to one-fourth of what it was.

Question 35

Consider two copper wires of equal cross-sectional area.One wire has 3 times the length of the other.How do the resistivities of these two wires compare?

A)Both wires have the same resistivity.
B)The longer wire has 3 times the resistivity of the shorter wire.
C)The longer wire has 9 times times the resistivity of the shorter wire.
D)The longer wire has 27 times times the resistivity of the shorter wire.

Question 36

If a quantity you calculated has units of what is that quantity?

A)potential
B)resistivity
C)resistance
D)capacitance
E)current

Question 37

For the graph shown in the figure,what physical quantity does the slope of the graph represent for a dc circuit?

A)1/(resistance)
B)resistance
C)potential
D)(potential)²
E)1/(potential)

Question 38

A kilowatt-hour is equivalent to

A)1000 W.
B)3600 J.
C)3,600,000 J/s.
D)3,600,000 J.
E)3600 J/s

Question 39

The figure shows a graph of the power dissipated in a resistor as a function of the resistance.What quantity does the slope of this graph represent?

A)the current in the resistor
B)the potential difference across the resistor
C)the reciprocal of the current in the resistor
D)the square of the current in the resistor
E)the resistivity of the resistor

Question 40

For the graph shown in the figure,what physical quantity does the slope of the graph represent for a dc circuit?

A)resistivity
B)resistance
C)energy
D)current
E)capacitance

Question 41

You buy a AA battery in the store,and it is marked 1.5 V.If this marking is strictly accurate,while this battery is fresh

A)its terminal voltage will be more than 1.5 V when it is used in a circuit.
B)its terminal voltage will be less than 1.5 V when it is used in a circuit.
C)its terminal voltage will be 1.5 V when it is used in a circuit.

Question 42

A resistor is made out of a wire having a length L.When the ends of the wire are attached across the terminals of an ideal battery having a constant voltage V₀ across its terminals,there is current I through the wire.If the wire were cut in half,making two wires of length L/2,and both wires were attached across the terminals of the battery (the right ends of both wires attached to one terminal,and the left ends attached to the other terminal),how much current would the battery put out?

A)4I
B)2I
C)I
D)I/2
E)I/4

Question 43

Four unequal resistors are connected in a parallel with each other.Which one of the following statements is correct about this combination?

A)The equivalent resistance is less than that of the smallest resistor.
B)The equivalent resistance is equal to the average of the four resistances.
C)The equivalent resistance is midway between the largest and smallest resistance.
D)The equivalent resistance is more than the largest resistance.
E)None of the other choices is correct.

Question 44

As more resistors are added in parallel across a constant voltage source,the power supplied by the source

A)increases.
B)decreases.
C)does not change.
D)increases for a time and then starts to decrease.

Question 45

When different resistors are connected in parallel across an ideal battery,we can be certain that

A)there is the same current through each one.
B)the potential difference across each is the same.
C)the power dissipated in each is the same.
D)their equivalent resistance is greater than the resistance of any one of the individual resistances.
E)their equivalent resistance is equal to the average of the individual resistances.

Question 46

When unequal resistors are connected in parallel in a circuit,

A)there is always the same current through each resistor.
B)the potential drop is always the same across each resistor.
C)the largest resistance has the largest current through it.
D)the power generated in each resistor is the same.

Question 47

Identical ideal batteries are connected in different arrangements to the same light bulb,as shown in the figure.For which arrangement will the bulb shine the brightest?

A)A
B)B
C)C

Question 48

As more resistors are added in series to a constant voltage source,the power supplied by the source

A)increases.
B)decreases.
C)does not change.
D)increases for a time and then starts to decrease.

Question 49

In the circuit shown in the figure,the resistor R has a variable resistance.As R is decreased,what happens to the currents?

A)I₁ remains unchanged and I₂ increases.
B)I₁ decreases and I₂ decreases.
C)I₁ decreases and I₂ increases.
D)I₁ increases and I₂ decreases.
E)I₁ increases and I₂ increases.

Question 50

Four unequal resistors are connected in series with each other.Which one of the following statements is correct about this combination?

A)The equivalent resistance is equal to that of any one of the resistors.
B)The equivalent resistance is equal to average of the four resistances.
C)The equivalent resistance is less than that of the smallest resistor.
D)The equivalent resistance is less than that of the largest resistor.
E)The equivalent resistance is more than the largest resistance.

Question 51

Kirchhoff's loop rule is a statement of

A)the law of conservation of momentum.
B)the law of conservation of charge.
C)the law of conservation of energy.
D)the law of conservation of angular momentum.
E)Newton's second law.

Question 52

Draw a circuit consisting of a battery connected to two resistors,R₁ and R₂,in series with each other and a capacitor C connected across the resistors.

Question 53

A 9-V battery is hooked up to two resistors in series using wires of negligible resistance.One has a resistance of 5 Ω,and the other has a resistance of 10 Ω.Several locations along the circuit are marked with letters,as shown in the figure.Which statements about this circuit are true? (There could be more than one correct choice.)

A)The current is exactly the same at points A, B, C, and D.
B)The current at A is greater than the current at B, which is equal to the current at C, which is greater than the current at D.
C)The current at A is greater than the current at B, which is greater than the current at C, which is greater than the current at D.
D)The potential at B is equal to the potential at C.
E)The potential at D is equal to the potential at C.

Question 54

Draw a circuit with a battery connected to four resistors,R₁,R₂,R₃,and R₄,as follows.Resistors R₁ and R₂ are connected in parallel with each other,resistors R₃ and R₄ are connected in parallel with each other,and both parallel sets of resistors are connected in series with each other across the battery.

Question 55

The lamps in a string of decorative lights are connected in parallel across a constant-voltage power source.What happens if one lamp burns out? (Assume negligible resistance in the wires leading to the lamps.)

A)The brightness of the lamps will not change appreciably.
B)The other lamps get brighter equally.
C)The other lamps get brighter, but some get brighter than others.
D)The other lamps get dimmer equally.
E)The other lamps get dimmer, but some get dimmer than others.

Question 56

Kirchhoff's junction rule is a statement of

A)the law of conservation of momentum.
B)the law of conservation of charge.
C)the law of conservation of energy.
D)the law of conservation of angular momentum.
E)Newton's second law.

Question 57

Draw a circuit with two batteries,a resistor between them,and a capacitor in parallel with the resistor.The batteries are connected negative pole to positive pole.

Question 58

You obtain a 100-W light bulb and a 50-W light bulb.Instead of connecting them in the normal way,you devise a circuit that places them in series across normal household voltage.If each one is an incandescent bulb of fixed resistance,which statement about these bulbs is correct?

A)Both bulbs glow with the same brightness, but less than their normal brightness.
B)Both bulbs glow with the same brightness, but more than their normal brightness.
C)The 100-W bulb glows brighter than the 50-W bulb.
D)The 50-W bulb glows more brightly than the 100-W bulb.

Question 59

A 9-V battery is hooked up to two resistors in series.One has a resistance of 5 Ω,and the other has a resistance of 10 Ω.Several locations along the circuit are marked with letters,as shown in the figure.Which resistor is converting electric energy into internal energy at the higher rate?

A)the 10-Ω resistor
B)the 5-Ω resistor
C)Energy is being dissipated by both resistors at the same rate.

Question 60

When unequal resistors are connected in series across an ideal battery,

A)the same power is dissipated in each one.
B)the potential difference across each is the same.
C)the current through each is the same.
D)the equivalent resistance of the circuit is less than that of the smallest resistor.
E)the equivalent resistance of the circuit is equal to the average of all the resistances.

Question 61

If a charge of 11.4 C passes through a computer in 1.75 min,what is the average current through the computer?

Question 62

A 4000-Ω resistor is connected across a 220-V power source.What is the current through the resistor?

A)0.055 A
B)1.8 A
C)5.5 A
D)18 A

Question 63

If 3.0 × 10¹⁵ electrons flow through a section of a wire of diameter 2.0 mm in 4.0 s,what is the current through the wire? (e = 1.60 × 10^-19 C)

A)0.12 mA
B)0.24 mA
C)7.5 × 10⁷ A
D)7.5 × 10¹⁴ A

Question 64

The current through a piece of lab equipment must be limited to 2.75 A when it is run by a 120-V dc power supply.What must be the resistance of this equipment?

Question 65

What potential difference is required across an 8.0-Ω resistor to cause a 2.0 A current through it?

Question 66

What potential difference is required to cause 4.00 A of current through a resistance of 330 Ω?

A)12.1 V
B)82.5 V
C)334 V
D)1320 V

Question 67

A total of 2.0 × 10¹³ electrons pass a given point in a wire in 15 s.What is the current through the wire? (e = 1.60 × 10^-19 C)

A)1.3 mA
B)1.3 A
C)0.21 μA
D)3.2 μA

Question 68

There is a 10-A current through a wire for 2.0 min.(e = 1.60 × 10^-19 C)
(a)How much charge has passed through this wire?
(b)How many electrons have passed any point in the wire?

Question 69

A electric heater that draws 13.5 A of dc current has been left on for 10 min.How many electrons that have passed through the heater during that time? (e = 1.60 × 10^-19 C)

A)1.5 × 10²²
B)5.1 × 10²²
C)1.8 × 10³
D)8.1 × 10³
E)1.0 × 10²³

Question 70

There is a current of 5.0 A through an electrical device for 10 seconds.How many electrons flow through this device during this time? (e = 1.60 × 10^-19 C)

A)0.20
B)20
C)2.0
D)3.1 x
E)31 x

Question 71

How much charge must pass by a point in a wire in 10 s for the current through the wire to be 0.50 A?

A)20 C
B)2.0 C
C)5.0 C
D)0.050 C

Question 72

A light bulb operating at 110 V draws 1.40 A of current.What is its resistance?

A)12.7 Ω
B)78.6 Ω
C)109 Ω
D)154 Ω

Question 73

A charge of 12 C passes through an electroplating apparatus in 2.0 min.What is the average current through the apparatus?

A)0.10 A
B)0.60 A
C)1.0 A
D)6.0 A

Question 74

A jeweler needs to electroplate gold,having an atomic mass of 196.97 g/mol,onto a bracelet.He knows that the charge carriers in the ionic solution are singly-ionized gold ions,Au⁺,and has calculated that he must deposit of gold to reach the necessary thickness.How much current does he need to plate the bracelet in 3.0 hours? (e = 1.60 × 10^-19 C,N_A = 6.02 × 10²³ atoms/mol)

A)9.1 mA
B)540 mA
C)33 A
D)1800 mA

Question 75

In an electroplating process,it is desired to deposit 40 mg of silver on a metal part by using a current of 2.0 A.How long must the current be allowed to run to deposit this much silver? The silver ions are singly charged,and the atomic mass of silver is 108 g/mol.(e = 1.60 × 10^-19 C,N_A = 6.02 × 10²³ atoms/mol)

A)16 s
B)18 s
C)20 s
D)22 s

Question 76

For the circuit shown in the figure,write the Kirchhoff current equation for the node labeled A.Notice the directions of the currents!

Question 77

What is the current through a resistor if 4.0 × 10¹⁶ electrons pass a point in the resistor in 0.50 s? (e = 1.60 × 10^-19 C)

A)0.013 A
B)0.31 A
C)6.3 A
D)78 A

Question 78

What is the current through a wire if 0.67 C of charge pass a point in the wire in 0.30 s?

A)2.2 A
B)0.67 A
C)0.30 A
D)0.20 A

Question 79

For the circuit shown in the figure,write the Kirchhoff loop equation for the entire outside loop.Notice the directions of the currents!

Question 80

What is the voltage across a 5.0-Ω resistor if the current through it is 5.0 A?

A)100 V
B)25 V
C)4.0 V
D)1.0 V