Deck 18: Electric Currents

Question 1

Choose the one alternative that best completes the statement or answers the question.
For the graph shown in the figure, what physical quantity does the slope of the graph represent for ohmic material?

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

Answer 1

C

Question 2

Choose the one alternative that best completes the statement or answers the question.
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 is $1 / 2$ as large.
B) It stays the same.
C) It is 4 times as large.
D) It is $1 / 4$ as large.
E) It is 2 times as large.

Answer 2

A

Question 3

Choose the one alternative that best completes the statement or answers the question.
Which one of the following quantities is equivalent to $1 \mathrm {~W}$ ?

A) $1 \mathrm {~A} \cdot \mathrm { s }$
B) $1 \mathrm {~V} / \Omega$
C) $1 \Omega \cdot \mathrm { m }$
D) $1 \mathrm {~V} / \mathrm { A }$
E) $1 \mathrm {~V} \cdot \mathrm { A }$

Answer 3

E

Question 4

Choose the one alternative that best completes the statement or answers the question.
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 product of the resistivity and the cross-sectional area of the wire
B) the reciprocal of the resistivity of the material
C) the cross-sectional area of the wire
D) the resistivity of the material of which the wire is made
E) the resistivity of the material divided by the cross-sectional area of the wire

Question 5

Choose the one alternative that best completes the statement or answers the question.
A kilowatt-hour is equivalent to

A) $3,600,000 \mathrm {~J} / \mathrm { s }$ .
B) $1000 \mathrm {~W}$ .
C) $3600 \mathrm {~J} / \mathrm { s }$
D) $3,600,000 \mathrm {~J}$ .
E) $3600 \mathrm {~J}$ .

Question 6

Choose the one alternative that best completes the statement or answers the question.
The figure shows conventional current passing through a resistor. The arrow shows the direction in which this conventional current is flowing. Which of the following statements are correct? (There could be more than one correct choice.)

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

Question 7

Choose the one alternative that best completes the statement or answers the question.
For the graph shown in the figure, what physical quantity does the slope of the graph represent for ohmic material?

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

Question 8

Choose the one alternative that best completes the statement or answers the question.
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 losing electric potential energy as they move through the resistor from $a$ to $b$ .
B) The speed of the electrons at point $b$ is the same as it is at point $a$ .
C) The electric potential is lower at point $b$ than at point $a$ .
D) The electric potential is higher at point $b$ than at point $a$ .
E) The electrons are moving slower at point $b$ than at point $a$ .

Question 9

Choose the one alternative that best completes the statement or answers the question.
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 9 times the resistance of the thinner wire.
C) The thicker wire has 3 times the resistance of the thinner wire.
D) The thicker wire has $1 / 9$ the resistance of the thinner wire.
E) The thicker wire has $\sqrt { 3 }$ times the resistance of the thinner wire.

Question 10

Choose the one alternative that best completes the statement or answers the question.
A wire of resistivity @ 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-fourth the original diameter.
C) be four times the original diameter.
D) be two times the original diameter.
E) be one-half the original diameter.

Question 11

Choose the one alternative that best completes the statement or answers the question.
For the graph shown in the figure, what physical quantity does the slope of the graph represent for ohmic material?

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

Question 12

Choose the one alternative that best completes the statement or answers the question.
Copper wire #1 has a length $L$ and a radius $b$ . Copper wire #2 has a length $2 L$ and a radius $2 b$ . Which statement about the resistance across the ends of the wires is true?

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

Question 13

Choose the one alternative that best completes the statement or answers the question.
If a quantity you calculated has units of $\frac { \mathrm { kg } \cdot \mathrm { m } ^ { 3 } } { \mathrm {~s} \cdot \mathrm { C } ^ { 2 } }$ what is that quantity?

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

Question 14

Choose the one alternative that best completes the statement or answers the question.
If a quantity you calculated has units of $\frac { \mathrm { kg } \cdot \mathrm { m } ^ { 2 } } { \mathrm {~s} \cdot \mathrm { C } ^ { 2 } }$ what is that quantity?

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

Question 15

Choose the one alternative that best completes the statement or answers the question.
For the graph shown in the figure, what physical quantity does the slope of the graph represent for a dc circuit?

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

Question 16

Choose the one alternative that best completes the statement or answers the question.
The length of a certain wire is doubled while its radius is kept constant. What is the new resistance of this wire? A) It is 3 times as large.
B) It is 2 times as large.
C) It stays the same.
D) It is $1 / 2$ as large.
E) It is 4 times as large.

Question 17

Choose the one alternative that best completes the statement or answers the question.
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 square of the current in the resistor
B) the potential difference across the resistor
C) the reciprocal of the current in the resistor
D) the current in the resistor
E) the resistivity of the resistor

Question 18

Choose the one alternative that best completes the statement or answers the question.
For the graph shown in the figure, what physical quantity does the slope of the graph represent for a dc circuit?

A) resistance
B) resistivity
C) $1 /$ (current)
D) current
E) $1 /$ (resistance)

Question 19

Choose the one alternative that best completes the statement or answers the question.
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 4 times as large.
B) It is $1 / 2$ as large.
C) It it 8 times as large.
D) It is 6 times as large.
E) It is 2 times as large.

Question 20

Choose the one alternative that best completes the statement or answers the question.
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) $3 \mathrm {~cm} \times 5 \mathrm {~cm}$ .
B) $5 \mathrm {~cm} \times 8 \mathrm {~cm}$ .
C) $3 \mathrm {~cm} \times 8 \mathrm {~cm}$ .
D) Any pair of faces produces the same resistance.

Question 21

Choose the one alternative that best completes the statement or answers the question.
Over ordinary temperature ranges, the resistance of most metals such as copper A) is a maximum at $20 ^ { \circ } \mathrm { C }$ .
B) increases as the metal gets hotter.
C) is independent of the temperature of the metal.
D) decreases as the metal gets hotter.

Question 22

Write the word or phrase that best completes each statement or answers the question.
The current through a piece of lab equipment must be limited to $2.75 \mathrm {~A}$ when it is run by a 120- $\mathrm { V }$ dc power supply. What must be the resistance of this equipment?

Question 23

Choose the one alternative that best completes the statement or answers the question.
A jeweler needs to electroplate gold, having an atomic mass of $196.97 \mathrm {~g} / \mathrm { mol }$ , onto a bracelet. He knows that the charge carriers in the ionic solution are singly-ionized gold ions, $\mathrm { Au } ^ { + }$ , and has calculated that he must deposit $0.20 \mathrm {~g}$ of gold to reach the necessary thickness. How much current does he need to plate the bracelet in $3.0$ hours? $\left( e = 1.60 \times 10 ^ { - 19 } \mathrm { C } , \mathrm { N } _ { \mathrm { A } } = 6.02 \times 10 ^ { 23 } \right.$ atoms/mol)

A) $540 \mathrm {~mA}$
B) $33 \mathrm {~A}$
C) $1800 \mathrm {~mA}$
D) $9.1 \mathrm {~mA}$

Question 24

Choose the one alternative that best completes the statement or answers the question.
A charge of $12 \mathrm { C }$ passes through an electroplating apparatus in $2.0 \mathrm {~min}$ . What is the average current in the apparatus?

A) $6.0 \mathrm {~A}$
B) $0.10 \mathrm {~A}$
C) $0.60 \mathrm {~A}$
D) $1.0 \mathrm {~A}$

Question 25

Choose the one alternative that best completes the statement or answers the question.
For the graph shown in the figure, what physical quantity does the slope of the graph represent for a dc circuit?

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

Question 26

Choose the one alternative that best completes the statement or answers the question.
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) $1 /$ (potential)
C) $( \text { potential } ) ^ { 2 }$
D) resistance
E) potential

Question 27

Choose the one alternative that best completes the statement or answers the question.
In an electroplating process, it is desired to deposit $40 \mathrm { mg }$ of silver on a metal part by using a current of $2.0 \mathrm {~A}$ . 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 $108 \mathrm {~g} / \mathrm { mol } . \left( e = 1.60 \times 10 ^ { - 19 } \mathrm { C } _ { \mathrm { A } } = \right.$ $6.02 \times 10 ^ { 23 }$ atoms $/ \mathrm { mol }$ )

A) $20 \mathrm {~s}$
B) $18 \mathrm {~s}$
C) $16 \mathrm {~s}$
D) $22 \mathrm {~s}$

Question 28

Choose the one alternative that best completes the statement or answers the question.
A current of $5.0$ A flows through an electrical device for 10 seconds. How many electrons flow through this device during this time? $\left( e = 1.60 \times 10 ^ { - 19 } \mathrm { C } \right)$

A) 20
B) $0.20$
C) $31 \times 10 ^ { 20 }$
D) $3.1 \times 10 ^ { 20 }$
E) $2.0$

Question 29

Choose the one alternative that best completes the statement or answers the question.
If $3.0 \times 10^{15}$ electrons flow through a section of a wire of diameter $2.0 \mathrm {~mm}$ in $4.0 \mathrm {~s}$ , what is the current in the wire? $\left( e = 1.60 \times 10 ^ { - 19 } \mathrm { C } \right)$

A) $7.5 \times 10 ^ { 14 } \mathrm {~A}$
B) $0.12 \mathrm {~mA}$
C) $0.24 \mathrm {~mA}$
D) $7.5 \times 10 ^ { 7 } \mathrm {~A}$

Question 30

Choose the one alternative that best completes the statement or answers the question.
A total of $2.0 \times 10 ^ { 13 }$ electrons pass a given point in a wire in $15 \mathrm {~s}$ . What is the current in the wire? $\left( e = 1.60 \times 10 ^ { - 19 } \mathrm { C } \right)$

A) $1.3 \mathrm {~mA}$
B) $1.3 \mathrm {~A}$
C) $3.2 \mu \mathrm { A }$
D) $0.21 \mu \mathrm { A }$

Question 31

Write the word or phrase that best completes each statement or answers the question.
If a charge of $11.4 \mathrm { C }$ passes through a computer in $1.75 \mathrm {~min}$ , what is the average current through the computer?

Question 32

Choose the one alternative that best completes the statement or answers the question.
A light bulb operating at 110 V draws 1.40 A of current. What is its resistance? A) $154 \Omega$
B) $109 \Omega$
C) $12.7 \Omega$
D) $78.6 \Omega$

Question 33

Choose the one alternative that best completes the statement or answers the question.
A electric heater that draws $13.5 \mathrm {~A}$ of dc current has been left on for $10 \mathrm {~min}$ . How many electrons that have passed through the heater during that time? (e $\left. = 1.60 \times 10 ^ { - 19 } \mathrm { C } \right)$

A) $8.1 \times 10 ^ { 3 }$
B) $5.1 \times 10 ^ { 22 }$
C) $1.0 \times 10 ^ { 23 }$
D) $1.5 \times 10 ^ { 22 }$
E) $1.8 \times 10 ^ { 3 }$

Question 34

Choose the one alternative that best completes the statement or answers the question.
A $12 - \mathrm { V }$ battery is connected across a $100 - \Omega$ resistor. How many electrons flow through the wire in $1.0 \mathrm {~min}$ ? $\left( e = 1.60 \times 10 ^ { - 19 } \mathrm { C } \right)$

A) $2.5 \times 10^{19}$
B) $4.5 \times 10 ^ { 19 }$
C) $3.5 \times 10 ^ { 19 }$
D) $1.5 \times 10 ^ { 19 }$

Question 35

Write the word or phrase that best completes each statement or answers the question.
A $10 -$ A current flows through a wire for $2.0 \mathrm {~min} . \left( e = 1.60 \times 10 ^ { - 19 } \mathrm { C } \right)$
(a) How much charge has passed through this wire?
(b) How many electrons have passed any point in the wire?

Question 36

Choose the one alternative that best completes the statement or answers the question.
What current is flowing in a resistor if 4.0 × 1016 electrons pass a point in the resistor in 0.50 s? (e = $1.60 \times 10 ^ { - 19 } \mathrm { C }$ )

A) $6.3 \mathrm {~A}$
B) $78 \mathrm {~A}$
C) $0.013 \mathrm {~A}$
D) $0.31 \mathrm {~A}$

Question 37

Choose the one alternative that best completes the statement or answers the question.
What potential difference is required to cause $4.00$ A to flow through a resistance of $330 \Omega$ ?

A) $1320 \mathrm {~V}$
B) $334 \mathrm {~V}$
C) $12.1 \mathrm {~V}$
D) $82.5 \mathrm {~V}$

Question 38

Choose the one alternative that best completes the statement or answers the question.
What current is flowing in a wire if $0.67 \mathrm { C }$ of charge pass a point in the wire in $0.30 \mathrm {~s}$ ?

A) $2.2 \mathrm {~A}$
B) $0.20 \mathrm {~A}$
C) $0.30 \mathrm {~A}$
D) $0.67 \mathrm {~A}$

Question 39

Write the word or phrase that best completes each statement or answers the question.
What potential difference is required across an 8.0-Ω resistor to cause 2.0 A to flow
through it?

Question 40

Write the word or phrase that best completes each statement or answers the question.
The graph shown in the figure shows the results of measurements of the dc current through a circuit device for various potential differences across it. Assume that all the numbers shown are accurate to two significant figures. What is the resistance of this device?

Question 41

Choose the one alternative that best completes the statement or answers the question.
How much current will flow through a 40.0-m length of metal wire with a radius of $0.0 \mathrm {~mm}$ if it is connected to a power source supplying $16.0 \mathrm {~V}$ ? The resistivity of the metal is $1.68 \times 10 ^ { - 8 } \Omega \cdot \mathrm { m }$ .

A) $0 \mathrm {~A}$
B) $0 \mathrm {~A}$
C) $0 \mathrm { nA }$
D) $0 \times 10 ^ { 8 } \mathrm {~A}$

Question 42

Choose the one alternative that best completes the statement or answers the question.
A certain metal wire has a cross-sectional area of $1.0 \mathrm {~cm} ^ { 2 }$ and a resistivity of $1.7 \times 10 ^ { - 8 } \Omega \cdot \mathrm { m }$ . How long would it have to be to have a resistance of $1.0 \Omega$ ?

A) $5.9 \times 10 ^ { 4 } \mathrm {~m}$
B) $5.9 \mathrm {~m}$
C) $5.9 \times 10 ^ { 6 } \mathrm {~m}$
D) $5.9 \mathrm {~km}$
E) $590 \mathrm {~m}$

Question 43

Choose the one alternative that best completes the statement or answers the question.
A $120 - \mathrm { m }$ long metal wire having a resistivity of $1.68 \times 10 ^ { - 8 } \Omega \cdot \mathrm { m }$ has a resistance of $6.0 \Omega$ . What is the diameter of the wire?

A) $0.65 \mathrm {~cm}$
B) $0.65 \mathrm {~m}$
C) $0.065 \mathrm {~mm}$
D) $0.65 \mathrm {~mm}$

Question 44

Choose the one alternative that best completes the statement or answers the question.
A certain metal has a resistivity of $1.68 \times 10 ^ { - 8 } \Omega \cdot \mathrm { m }$ . You have a long spool of wire made from this metal. If this wire has a diameter of $0.15 \mathrm {~mm}$ , how long should you cut a segment so its resistance will be $15 \Omega$ ?

A) $16 \mathrm {~m}$
B) $1.6 \mathrm {~m}$
C) $16 \mathrm {~mm}$
D) $16 \mathrm {~cm}$

Question 45

Choose the one alternative that best completes the statement or answers the question.
When a potential difference is applied across a piece of wire made of metal A, a $5.0 - \mathrm { mA }$ current flows. If the metal-A wire is replaced with a wire made of metal B having twice the diameter of the metal-A wire, how much current will flow through the metal-B wire? The lengths of both wires are the same, and the voltage difference remains unchanged. The resistivity of metal $\mathrm { A }$ is $1.68 \times 10 ^ { - 8 } \Omega \cdot \mathrm { m }$ , and the resistivity of metal $B$ is $1.59 \times 10 ^ { - 8 } \Omega \cdot \mathrm { m }$ .

A) $19 \mathrm {~mA}$
B) $21 \mathrm {~mA}$
C) $11 \mathrm {~mA}$
D) $5.3 \mathrm {~mA}$

Question 46

Choose the one alternative that best completes the statement or answers the question.
The resistivity of a $1.0 \mathrm {~m}$ long copper wire is $1.72 \times 10 ^ { - 8 } \Omega \cdot \mathrm { m }$ and its cross sectional area is $2.0 \times$ $10 ^ { - 6 } \mathrm {~m} ^ { 2 }$ . If the wire carries a current of $0.20 \mathrm {~A}$ , what is the voltage across the wire?

A) $1.7 \mathrm { mV }$
B) $17 \mathrm { mV }$
C) $0.90 \mathrm { mV }$
D) $90 \mathrm { mV }$
E) $10 \mathrm { mV }$

Question 47

Choose the one alternative that best completes the statement or answers the question.
The resistance of a $100 - \mathrm { cm }$ wire of cross sectional area $2 \times 10 ^ { - 6 } \mathrm {~m} ^ { 2 }$ is $400 \Omega$ . What is the resistivity of the material from which this wire is made?

A) $0.80 \times 10 ^ { - 5 } \Omega \cdot \mathrm { m }$
B) $0.80 \times 10 ^ { - 6 } \Omega \cdot \mathrm { m }$
C) $8.0 \times 10 ^ { - 4 } \Omega \cdot \mathrm { m }$
D) $8.0 \times 10 ^ { - 6 } \Omega \mathrm { V }$
E) $0.80 \times 10 ^ { - 4 } \Omega \cdot \mathrm { m }$

Question 48

Choose the one alternative that best completes the statement or answers the question.
What is the resistance of $1.0 \mathrm {~m}$ of a solid cylindrical metal cable having a diameter of $0.40$ inches and a resistivity of $1.68 \times 10 ^ { - 8 } \Omega \cdot \mathrm { m }$ ?

A) $0.00021 \Omega$
B) $0.0012 \Omega$
C) $0.0021 \Omega$
D) $0.00012 \Omega$

Question 49

Write the word or phrase that best completes each statement or answers the question.
The graph shown in the figure shows the results of measurements of the dc current through a circuit device for various potential differences across it. Assume that all the numbers shown are accurate to two significant figures. What is the resistance of this device?

Question 50

Choose the one alternative that best completes the statement or answers the question.
A $1.0 - \mathrm { m }$ length of nichrome wire has a radius of $0.50 \mathrm {~mm}$ and a resistivity of $1.0 \times 10 ^ { - 6 } \Omega \cdot \mathrm { m }$ . When this wire carries a current of $0.50 \mathrm {~A}$ , what is the voltage across its ends?

A) $1.6 \mathrm {~V}$
B) $0.0030 \mathrm {~V}$
C) $0.64 \mathrm {~V}$
D) $0.32 \mathrm {~V}$

Question 51

Choose the one alternative that best completes the statement or answers the question.
A rod is $4.0 \mathrm {~m}$ long and has a square cross-section that is $1.5 \mathrm {~cm}$ on each side. An ohmmeter measures $0.040 \Omega$ across its ends. What is the resistivity of the material from which this rod is made?

A) $0.015 \Omega \cdot \mathrm { m }$
B) $2.3 \times 10 ^ { - 6 } \Omega \cdot \mathrm { m }$
C) $0.023 \Omega \cdot \mathrm { m }$
D) $1.5 \times 10 ^ { - 4 } \Omega \cdot \mathrm { m }$

Question 52

Write the word or phrase that best completes each statement or answers the question.
When a thin copper wire that is $178 \mathrm {~m}$ long is connected between a $1.2 - \mathrm { V }$ potential difference, a current of $2.0$ amps flows through the wire. What is the diameter of this wire? The resistivity of copper is $1.72 \times 10 ^ { - 8 } \Omega \cdot \mathrm { m }$ .

Question 53

Choose the one alternative that best completes the statement or answers the question.
The resistivity of the material of a wire is $1.76 \times 10 ^ { - 8 } \Omega \cdot \mathrm { m }$ . If the diameter of the wire is $2.00 \mathrm {~mm}$ and its length is $2.00 \mathrm {~m}$ , what is its resistance?

A) $11.2 \Omega$
B) $1.12 \Omega$
C) $0.0112 \Omega$
D) $112 \Omega$
E) $0.112 \Omega$

Question 54

Choose the one alternative that best completes the statement or answers the question.
When a 1.0-m length of metal wire is connected to a $1.5 - \mathrm { V }$ battery, a current of $8.0 \mathrm {~mA}$ flows through it. What is the diameter of the wire? The resistivity of the metal is $2.24 \times 10 ^ { - 8 } \Omega \cdot \mathrm { m }$ .

A) $12 \mu \mathrm { m }$
B) $24 \mu \mathrm { m }$
C) $6.0 \mu \mathrm { m }$
D) $2.2 \mu \mathrm { m }$

Question 55

Choose the one alternative that best completes the statement or answers the question.
A $1.0 - \mathrm { mm }$ diameter extension cord is made of metal having a resistivity of $1.68 \times 10 ^ { - 8 } \Omega \cdot \mathrm { m }$ . When it carries a current of $15 \mathrm {~A}$ , what is the potential difference between two points in the cord that are $100 \mathrm {~m}$ apart?

A) $41 \mathrm {~V}$
B) $32 \mathrm {~V}$
C) $23 \mathrm {~V}$
D) $12 \mathrm {~V}$

Question 56

Choose the one alternative that best completes the statement or answers the question.
How much current will be flowing through a $57.0 - \mathrm { m }$ length of copper wire with radius $0.0$ mm if it is connected to a source supplying $62.0 \mathrm {~V}$ ? The resistivity of the metal is $1.68 \times 10 ^ { - 8 } \Omega \cdot \mathrm { m }$ .

A) $0 \mathrm { nA }$
B) $0 \mathrm {~A}$
C) $0 \mathrm {~A}$
D) $0 \times 10 ^ { 8 } \mathrm {~A}$

Question 57

Write the word or phrase that best completes each statement or answers the question.
A 25-m wire of diameter $0.30 \mathrm {~mm}$ draws $0.499 \mathrm {~A}$ when connected across a $3.0$ - $\mathrm { V }$ potential difference.
(a) What is the resistance of the wire?
(b) What is the resistivity of the material from which the wire is made?

Question 58

Choose the one alternative that best completes the statement or answers the question.
What is the resistance of a cylindrical metal rod $1.0 \mathrm {~cm}$ in diameter and $45 \mathrm {~m}$ long, if the resistivity of the metal is $1.4 \times 10 ^ { - 8 } \Omega \cdot \mathrm { m }$ ?

A) $0.0080 \Omega$
B) $0.0063 \Omega$
C) $6.3 \Omega$
D) $0.80 \Omega$

Question 59

Choose the one alternative that best completes the statement or answers the question.
The resistivity of gold is $2.44 \times 10 ^ { - 8 } \Omega \cdot \mathrm { m }$ at a temperature of $20 ^ { \circ } \mathrm { C }$ . A gold wire that is $0.50 \mathrm {~mm}$ in diameter and $44 \mathrm {~cm}$ long carries a current of $380 \mathrm {~mA}$ . How many electrons each second pass a given cross section of the wire at $20 ^ { \circ } \mathrm { C } ? \left( e = 1.60 \times 10 ^ { - 19 } \mathrm { C } \right)$

A) $2.4 \times 10 ^ { 18 }$
B) $2.4 \times 10 ^ { 17 }$
C) $6.3 \times 10 ^ { 15 }$
D) $2.8 \times 10 ^ { 14 }$
E) $1.2 \times 10 ^ { 22 }$

Question 60

Choose the one alternative that best completes the statement or answers the question.
A metal bar is $20 \mathrm {~cm}$ long and has a rectangular cross-section measuring $1.0 \mathrm {~cm} \times 2.0 \mathrm {~cm}$ . What is the voltage drop along its length when it carries a 4000-A current? The resistivity of the metal is $1.68 \times 10 ^ { - 8 } \Omega \cdot \mathrm { m }$ .

A) $0.034 \mathrm {~V}$
B) $0.67 \mathrm {~V}$
C) $0.067 \mathrm {~V}$
D) $0.34 \mathrm {~V}$

Question 61

Write the word or phrase that best completes each statement or answers the question.
What is the resistance of a 0.100-kW light bulb designed to be used in a 120-V circuit dc? A) $1.2 \Omega$
B) $0.83 \Omega$
C) $12.0 \Omega$
D) $144 \Omega$

Question 62

Write the word or phrase that best completes each statement or answers the question.
If the power rating of a $400 - \Omega$ resistor is $0.800 \mathrm {~W}$ , what is the maximum voltage that can safely be connected across the resistor?

A) $170 \mathrm {~V}$
B) $17.9 \mathrm {~V}$
C) $110 \mathrm {~V}$
D) $1.80 \mathrm {~V}$

Question 63

Write the word or phrase that best completes each statement or answers the question.
How much does it cost to operate a 25-W soldering iron for 8.0 hours if energy costs 8.0¢/kWh? A) $16 \phi$
B) $25 \phi$
C) $\$ 1.50$
D) $1.6 \phi$

Question 64

Write the word or phrase that best completes each statement or answers the question.
How much energy does a 100-W light bulb use in 8.0 hours? A) $0.0080 \mathrm { kWh }$
B) $13 \mathrm { kWh }$
C) $0.80 \mathrm { kWh }$
D) $800 \mathrm { kWh }$

Question 65

Write the word or phrase that best completes each statement or answers the question.
A light bulb operating at a dc voltage of $120 \mathrm {~V}$ has a power rating of $60 \mathrm {~W}$ . How much current is flowing through this bulb?

A) $1.5 \mathrm {~A}$
B) $2.5 \mathrm {~A}$
C) $1.0 \mathrm {~A}$
D) $0.50 \mathrm {~A}$
E) $2.0 \mathrm {~A}$

Question 66

Write the word or phrase that best completes each statement or answers the question.
If the power rating of a $400 - \Omega$ resistor is $0.80 \mathrm {~W}$ , what is the maximum current it can safely draw?

A) $45 \mathrm {~mA}$
B) $320 \mathrm {~mA}$
C) $4.4 \mathrm {~mA}$
D) $18 \mathrm {~mA}$
E) $2.0 \mathrm {~mA}$

Question 67

Write the word or phrase that best completes each statement or answers the question.
A flashlight draws $0.133$ A from a $3.0$ - $V$ battery pack. In $2.0$ minutes (a) how much charge flows from the battery, (b) how much energy does the battery supply, and (c) how many electrons have passed any point in the circuit every second?

Question 68

Write the word or phrase that best completes each statement or answers the question.
A 1500-W heater is connected to a 120-V line for 2.0 hours. How much heat energy is produced? A) $3.0 \mathrm {~kJ}$
B) $11 \mathrm { MJ }$
C) $1.5 \mathrm {~kJ}$
D) $0.18 \mathrm { MJ }$

Question 69

Write the word or phrase that best completes each statement or answers the question.
A 25-W soldering iron runs on 110 V dc. What is its resistance? A) $0.0020 \Omega$
B) $2.8 \mathrm { k } \Omega$
C) $0.48 \mathrm { k } \Omega$
D) $4.4 \Omega$

Question 70

Write the word or phrase that best completes each statement or answers the question.
A 400-W computer (including its monitor) is turned on for 8.0 hours per day. If electricity costs 10¢ per kWh, how much does it cost to run the computer annually for a 365-day year? A) $\$ 1200$
B) $\$ 150$
C) $\$ 120$
D) $\$ 15$

Question 71

Write the word or phrase that best completes each statement or answers the question.
A toaster is rated at 800 W when operating at 120 V dc. What is the resistance of its heating element? A) $16 \Omega$
B) $18 \Omega$
C) $0.15 \Omega$
D) $6.7 \Omega$

Question 72

Write the word or phrase that best completes each statement or answers the question.
A 200-Ω resistor is rated at 1/4 W. What is the maximum current it can safely draw? A) $0.035 \mathrm {~A}$
B) $0.25 \mathrm {~A}$
C) $0.35 \mathrm {~A}$
D) $50 \mathrm {~A}$

Question 73

Write the word or phrase that best completes each statement or answers the question.
When a 14.0-A current flows through an 8.00-Ω device for 24.0 hours, how much does this cost if energy costs $0.0900 per kW · h? A) $\$ 0.24$
B) $\$ 2.16$
C) $\$ 3.39$
D) $\$ 1.04$

Question 74

Choose the one alternative that best completes the statement or answers the question.
A tube of mercury with resistivity $9.84 \times 10 ^ { - 7 } \Omega \cdot \mathrm { m }$ has a uniform electric field of $23 \mathrm {~N} / \mathrm { C }$ inside the mercury. How much current is flowing in the tube, if the radius of the tube is $0.495 \mathrm {~mm}$ ?

A) $280 \mathrm {~A}$
B) $18 \mathrm {~A}$
C) $29 \mathrm {~A}$
D) $180 \mathrm {~A}$

Question 75

Write the word or phrase that best completes each statement or answers the question.
A 100-W driveway light bulb is on 10 hours per day. If the power company charges 10¢ for each kilowatt-hour of electricity used, estimate the yearly cost to operate the bulb if it is used every day
For a 365-day year. A) $\$ 73$
B) $\$ 37$
C) $\$ 7.30$
D) $\$ 3.65$

Question 76

Write the word or phrase that best completes each statement or answers the question.
A 100-W light bulb is operated by a 110-V dc source. What is the resistance of this bulb? A) $6.0 \times 10 ^ { - 3 } \Omega$
B) $240 \Omega$
C) $100 \Omega$
D) $120 \Omega$
E) $8.0 \times 10 ^ { - 3 } \Omega$

Question 77

Write the word or phrase that best completes each statement or answers the question.
A battery is rated at 12 V and 160 A-h. How much energy does this battery store? A) $1.9 \mathrm { MJ }$
B) $6.0 \mathrm {~kJ}$
C) $1.9 \mathrm {~kJ}$
D) $6.9 \mathrm { MJ }$

Question 78

Write the word or phrase that best completes each statement or answers the question.
The power rating of a $400 - \Omega$ resistor is $0.800 \mathrm {~W}$ .
(a) What is the maximum safe voltage across this resistor?
(b) What is the maximum current the resistor can safely draw?

Question 79

Write the word or phrase that best completes each statement or answers the question.
A resistor operated at $120 \mathrm {~V} \mathrm { dc }$ is rated at $1.40 \mathrm {~kW}$ .
(a) What is the normal operating current through the resistor?
(b) What is the resistance of the resistor?

Question 80

Write the word or phrase that best completes each statement or answers the question.
An instrument is rated at $250 \mathrm {~W}$ if it is connected across a $120 - \mathrm { V }$ dc power supply.
(a) What current does it draw under normal operation?
(b) What is its resistance?
(c) How many kilowatt-hours does it use in a day if it is left on all the time?