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.

Accepted Answer

In an ionic liquid such as salty water, there are both positive and negative ions present. When an electric current passes through the liquid, both positive and negative ions move towards opposite electrodes. Therefore, the moving charges are both positive and negative ions.

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

Accepted Answer

A ∙ s is the unit for electric charge, represented by the symbol Q.

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.

Accepted Answer

The resistance $R$ of a wire is given by $R = \rho \frac{L}{A}$, where $\rho$ is the resistivity, $L$ is the length, and $A$ is the cross-sectional area. If the length is quadrupled ($L' = 4L$) and the resistance is to remain constant, the area must also be quadrupled to keep $R$ constant. Since the area $A = \pi r^2 = \pi (\frac{d}{2})^2$, quadrupling the area means doubling the diameter.

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.

Accepted Answer

The answer of The figure shows electrons passing through 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)

Accepted Answer

The answer of For the graph shown in the figure,what...

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.

Accepted Answer

The answer of Copper wire #1 has a length L...

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)

Accepted Answer

The answer of For the graph shown in the figure,what...

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)

Accepted Answer

The answer of For the graph shown in the figure,what...

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.

Accepted Answer

The resistance of a wire is directly proportional to its length and inversely proportional to the square of its radius. Hence, when the radius is doubled, the resistance becomes 1/4th of its original value (since (2r)^2 = 4(r^2)). Therefore, the new resistance is increased by a factor of 4.

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.

Accepted Answer

Resistivity is a property of material and does not depend on the shape or size of the object made from that material. Therefore doubling the radius without changing the length, does not affect the resistivity of the wire.

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.

Accepted Answer

The moving charges in a metal wire when there is electric current are electrons. Electrons are negatively charged particles that are able to move through the metal lattice when a voltage is applied and a current is flowing.

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)

Accepted Answer

For an ohmic material, the slope of the graph represents resistance. This can be seen from Ohm's Law, which states that the current through a conductor is directly proportional to the voltage applied to it, and the constant of proportionality is the resistance of the conductor. Therefore, the slope of the graph is equal to the resistance (ΔV/ΔI).

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.

Accepted Answer

The resistance $R$ of a wire is directly proportional to its length $L$ and inversely proportional to the square of its radius $r$, as given by the formula $R = \rho \frac{L}{A}$, where $A = \pi r^2$ is the cross-sectional area and $\rho$ is the resistivity of the material. Doubling the length of the wire doubles its resistance, since the radius (and thus the cross-sectional area) remains constant.

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

Accepted Answer

The answer of The figure shows a graph of the...

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.

Accepted Answer

The answer of The length of a certain wire is...

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.

Accepted Answer

The resistance of a material is given by $R = \rho \frac{L}{A}$, where $\rho$ is the resistivity of the material, $L$ is the length through which the current flows, and $A$ is the cross-sectional area perpendicular to the current flow. To minimize resistance, you want to maximize the cross-sectional area and minimize the length. Attaching the leads to the opposite faces measuring 5 cm × 8 cm gives the largest cross-sectional area and the shortest length (3 cm), resulting in the smallest possible 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.

Accepted Answer

The answer of You are given a copper bar of...

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.

Accepted Answer

The answer of The figure shows conventional current through 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

Accepted Answer

The answer of If a quantity you calculated has units...

Question 20

If a quantity you calculated has units of $\frac { \mathrm { kg } \cdot \mathrm { m } ^ { 2 } } { \mathrm {~s} ^ { 2 } \cdot \mathrm { C } }$ ,what is that quantity?
A)potential
B)resistivity
C)resistance
D)capacitance
E)charge

Accepted Answer

The given units $\frac { \mathrm { kg } \cdot \mathrm { m } ^ { 2 } } { \mathrm {~s} ^ { 2 } \cdot \mathrm { C } }$ correspond to the unit of potential (voltage) in the International System of Units (SI), where kg is kilograms, m is meters, s is seconds, and C is coulombs. Potential is measured in volts, and 1 volt = 1 $\frac { \mathrm { kg } \cdot \mathrm { m } ^ { 2 } } { \mathrm {~s} ^ { 2 } \cdot \mathrm { C } }$.

Quiz 17: Dc Circuits

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

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

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

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.)

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

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?

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

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

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

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

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

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

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

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?

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?

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

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

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.)

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

If a quantity you calculated has units of kg⋅m2 s2⋅C\frac { \mathrm { kg } \cdot \mathrm { m } ^ { 2 } } { \mathrm {~s} ^ { 2 } \cdot \mathrm { C } } s2⋅Ckg⋅m2​ ,what is that quantity?

If a quantity you calculated has units of $\frac { \mathrm { kg } \cdot \mathrm { m } ^ { 2 } } { \mathrm {~s} ^ { 2 } \cdot \mathrm { C } }$ ,what is that quantity?