Question 1

At a certain instant the current flowing through a 5.0-H inductor is 3.0 A.If the energy in the inductor at this instant is increasing at a rate of 3.0 J/s,how fast is the current changing?

Accepted Answer

A)   0.20 A/s
B)   0.40 A/s
C)   0.10 A/s
D)   0.80 A/s A

Question 2

Which of the following statements about inductors are correct? There may be more than one correct choice.

Accepted Answer

A)   When it is connected in a circuit, an inductor always resists having current flow through it.
B)   Inductors store energy by building up charge.
C)   When an inductor and a resistor are connected in series with a DC battery, the current in the circuit is reduced to zero in one time constant.
D)   An inductor always resists any change in the current through it.
E)   When an inductor and a resistor are connected in series with a DC battery, the current in the circuit is zero after a very long time. D

Question 3

A 96-mH solenoid inductor is wound on a form 0.80 m in length and 0.10 m in diameter.A coil is tightly wound around the solenoid at its center.The coil's resistance is 9.9 ohms.The mutual inductance of the coil and solenoid is  At a given instant,the current in the solenoid is  and is decreasing at the rate of  At the given instant,what is the magnitude of the induced current in the coil? (μ0 = 4π × 10-7 T • m/A)

Accepted Answer

A)   7.8 μA
B)   6.3 μA
C)   9.4 μA
D)   11 μA
E)   13 μA A

Question 4

An insulated wire of diameter 1.0 mm and negligible resistance is wrapped tightly around a cylindrical core of radius 5.0 cm and length 30 cm to build a solenoid.What is the energy stored in this solenoid when a current I = 0.20 A flows through it? (μ0 = 4π × 10-7 T • m/A)

Accepted Answer

A)   1.2 × 10-4 J
B)   9.6 × 10-4 J
C)   4.8 × 10-4 J
D)   2.4 × 10-4 J
E)   5.9 × 10-5 J

Question 5

A solenoid of length 0.700 m having a circular cross-section of radius 5.00 cm stores 6.00 µJ of energy when a 0.400-A current runs through it.What is the winding density of the solenoid? (μ0 = 4π × 10-7 T • m/A)

Accepted Answer

A)   865 turns/m
B)   472 turns/m
C)   1080 turns/m
D)   104 turns/m
E)   327 turns/m

Question 6

An LR circuit contains an ideal 60-V battery,a 42-H inductor having no resistance,a 24-Ω resistor,and a switch S,all in series.Initially,the switch is open and has been open for a very long time.At time t = 0 s,the switch is suddenly closed.How long after closing the switch will the potential difference across the inductor be 24 V?

Accepted Answer

A)   1.6 s
B)   1.4 s
C)   1.8 s
D)   1.9 s
E)   2.1 s

Question 7

In the figure,the current in a solenoid having no appreciable resistance is flowing from b to a and is decreasing at a rate of 9.6 A/s.The self-induced emf in the solenoid is found to be 8.4 V.  (a)What is the self-inductance of the solenoid?
(b)Which point,a or b is at higher potential?

Accepted Answer

The answer of In the figure,the current in a solenoid...

Question 8

An LR circuit contains an ideal 60-V battery,a 51-H inductor having no resistance,a 21-Ω resistor,and a switch S,all in series.Initially,the switch is open and has been open for a very long time.At time t = 0 s,the switch is suddenly closed.When the voltage across the resistor is equal to the voltage across the inductor,what is the current in the circuit?

Accepted Answer

A)   1.4 A
B)   0.57 A
C)   1.1 A
D)   0.86 A
E)   1.7 A

Question 9

A 45-mH ideal inductor is connected in series with a 60-Ω resistor through an ideal 15-V DC power supply and an open switch.If the switch is closed at time t = 0 s,what is the current  later?

Accepted Answer

A)   250 mA
B)   650 mA
C)   550 mA
D)   280 mA
E)   850 mA

Question 10

What is the energy density in the magnetic field 25 cm from a long straight wire carrying a current of 12 A? (μ0 = 4π × 10-7 T • m/A)

Accepted Answer

A)   7.3 × 10-5 J/m3
B)   3.7 × 10-5 J/m3
C)   3.6 × 10-4 J/m3
D)   1.2 × 10-4 J/m3
E)   The density cannot be determined without knowing the volume.

Question 11

A series LR circuit contains an emf source of  having no internal resistance,a resistor,a  inductor having no appreciable resistance,and a switch.If the emf across the inductor is  of its maximum value  after the switch is closed,what is the resistance of the resistor?

Accepted Answer

A)   14 Ω
B)   1.9 Ω
C)   1.5 Ω
D)   5.0 Ω

Question 12

At what rate would the current in a 100-mH inductor have to change to induce an emf of 1000 V in the inductor?

Accepted Answer

A)   100 A/s
B)   1 A/s
C)   1000 A/s
D)   10,000 A/s
E)   10 A/s

Question 13

A series LR circuit consists of a 2.0-H inductor with negligible internal resistance,a 100-ohm resistor,an open switch,and a 9.0-V ideal power source.After the switch is closed,what is the maximum power delivered by the power supply?

Accepted Answer

A)   0.40 W
B)   81 W
C)   0.090 W
D)   8.1 W
E)   0.81 W

Question 14

A series circuit consists of a 0.55-H inductor with internal resistance of 8.0 Ω connected in series with a 4.0-Ω resistor,an open switch,and an ideal 12-V battery.
(a)When the switch is closed,what is the initial current through the 4.0-Ω resistor?
(b)What is the current through the 4.0-Ω resistor a very long time after the switch is closed?

Accepted Answer

The answer of A series circuit consists of a 0.55-H...

Question 15

For the circuit shown in the figure,the inductors have no appreciable resistance and the switch has been open for a very long time.  (a)The instant after closing the switch,what is the current through the 60.0-Ω resistor?
(b)The instant after closing the switch,what is the potential difference across the 15.0-mH inductor?
(c)After the switch has been closed and left closed for a very long time,what is the potential drop across the 60.0-Ω resistor?

Accepted Answer

The answer of For the circuit shown in the figure,the...

Question 16

Consider the circuit shown in the figure.The battery has emf ε = 25 volts and negligible internal resistance.The inductance is and the resistances are R₁= 12 Ω and .Initially the switch S is open and no currents flow.Then the switch is closed. (a)What is the current in the resistor R₁ just after the switch is closed? (b)After leaving the switch closed for a very long time,it is opened again.Just after it is opened,what is the current in R₁?

Accepted Answer

The answer of Consider the circuit shown in the figure.The...

Question 17

What resistance should be added in series with a 3.0-H inductor to complete an LR circuit with a time constant of  ?

Accepted Answer

A)   0.75 k Ω
B)   12 Ω
C)   0.75 Ω
D)   2.5 Ω

Question 18

A charged capacitor is connected to an ideal inductor.At time t = 0,the charge on the capacitor is equal to 6.00 μC.At time t = 2.00 ms the charge on the capacitor is zero for the first time.What is the amplitude of the current at that same instant?

Accepted Answer

A)   2.38 mA
B)   4.71 mA
C)   0.780 mA
D)   1.53 mA
E)   1.19 mA

Question 19

An LC circuit consists of a 3.4-µF capacitor and a coil with a self-inductance 0.080 H and no appreciable resistance.At t = 0 the capacitor has a charge of 5.4 µC and the current in the inductor is zero.
(a)How long after t = 0 will the current in the circuit be maximum?
(b)What will be this maximum current?

Accepted Answer

The answer of An LC circuit consists of a 3.4-µF...

Question 20

An ideal solenoid is 18.5 cm long,has a circular cross-section 2.20 cm in diameter,and contains 545 equally spaced thin windings.This solenoid is connected in a series circuit with an open switch,a 15.0-Ω resistor,and a battery of internal resistance 5.00 Ω and open-circuit terminal voltage of 25.0 V.(μ₀ = 4π × 10^-7 T • m/A) (a)What is the maximum amount of energy that the solenoid will store after closing the switch? (b)How long after closing the switch will it take for the stored energy in the solenoid to reach one-half of its maximum value?

Accepted Answer

The answer of An ideal solenoid is 18.5 cm long,has...

Exam 30: Inductance

At a certain instant the current flowing through a 5.0-H inductor is 3.0 A.If the energy in the inductor at this instant is increasing at a rate of 3.0 J/s,how fast is the current changing?

Which of the following statements about inductors are correct? There may be more than one correct choice.

An insulated wire of diameter 1.0 mm and negligible resistance is wrapped tightly around a cylindrical core of radius 5.0 cm and length 30 cm to build a solenoid.What is the energy stored in this solenoid when a current I = 0.20 A flows through it? (μ₀ = 4π × 10^-7 T • m/A)

A solenoid of length 0.700 m having a circular cross-section of radius 5.00 cm stores 6.00 µJ of energy when a 0.400-A current runs through it.What is the winding density of the solenoid? (μ₀ = 4π × 10^-7 T • m/A)

In the figure,the current in a solenoid having no appreciable resistance is flowing from b to a and is decreasing at a rate of 9.6 A/s.The self-induced emf in the solenoid is found to be 8.4 V. (a)What is the self-inductance of the solenoid? (b)Which point,a or b is at higher potential?

A 45-mH ideal inductor is connected in series with a 60-Ω resistor through an ideal 15-V DC power supply and an open switch.If the switch is closed at time t = 0 s,what is the current later?

What is the energy density in the magnetic field 25 cm from a long straight wire carrying a current of 12 A? (μ₀ = 4π × 10^-7 T • m/A)

A series LR circuit contains an emf source of having no internal resistance,a resistor,a inductor having no appreciable resistance,and a switch.If the emf across the inductor is of its maximum value after the switch is closed,what is the resistance of the resistor?

At what rate would the current in a 100-mH inductor have to change to induce an emf of 1000 V in the inductor?

A series LR circuit consists of a 2.0-H inductor with negligible internal resistance,a 100-ohm resistor,an open switch,and a 9.0-V ideal power source.After the switch is closed,what is the maximum power delivered by the power supply?

What resistance should be added in series with a 3.0-H inductor to complete an LR circuit with a time constant of ?

A charged capacitor is connected to an ideal inductor.At time t = 0,the charge on the capacitor is equal to 6.00 μC.At time t = 2.00 ms the charge on the capacitor is zero for the first time.What is the amplitude of the current at that same instant?