Question 1

The "back emf" of a motor refers to a source of voltage that:

Accepted Answer

The answer of The "back emf" of a motor refers...

Question 2

By what factor is the self-inductance of an air solenoid changed if only its cross-sectional area,A,multiplied by six?

Accepted Answer

The self-inductance of a solenoid is directly proportional to its cross-sectional area. Therefore, if the cross-sectional area is multiplied by six, the self-inductance is also multiplied by six.

Question 3

A rectangular loop (area = 0.30 m²)turns in a uniform magnetic field with B = 0.50 T.At an instant when the angle between the magnetic field and the normal to the plane of the loop is π/2 rads and increasing at the rate of 0.52 rad/s,what is the magnitude of the emf induced in the loop?

Accepted Answer

The answer of A rectangular loop (area = 0.30 m²)turns...

Question 4

By what factor is the self-inductance of an air solenoid changed if only its number of coil turns,N,is tripled?

Accepted Answer

The self-inductance of an air solenoid is directly proportional to the square of its number of turns. Therefore, if the number of coil turns is tripled (N → 3N), the self-inductance will increase by a factor of (3N)^2/N^2 = 9.

Question 5

When a voltage is generated by rotating a coil in a magnetic field at a constant rate,the period of the voltage equals the time that it takes for the coil to rotate through ________ radians.

Accepted Answer

The period of the voltage generated by rotating a coil in a magnetic field at a constant rate is equal to the time taken for the coil to complete one full rotation or 2π radians. Therefore, option D is the correct choice.

Question 6

In the United States,the value of ω for commercially generated power is ________ in SI units.

Accepted Answer

The answer of In the United States,the value of ω...

Question 7

What is the minimum frequency with which a 200-turn,flat coil of cross sectional area 380 cm² can be rotated in a uniform 32-mT magnetic field if the maximum value of the induced emf is to equal 7.9 V?

Accepted Answer

The induced emf in a coil of N turns rotating at an angular frequency ω in a magnetic field B is given by:

ε = NωBAcos(ωt)

The maximum value of ε occurs when cos(ωt) = 1. Therefore:

εmax = NωB̅A

where B̅ is the maximum (uniform) value of the magnetic field.

We can rearrange this equation to solve for the minimum angular frequency:

ωmin = εmax / (NBA̅)

Plugging in the given values, we have:

N = 200
A = 380 cm² = 0.038 m²
B̅ = 32 mT = 0.032 T
εmax = 7.9 V

Therefore:

ωmin = (7.9 V) / (200 × 0.038 m² × 0.032 T)

ωmin ≈ 5.16 Hz

So the minimum frequency at which the coil can be rotated to achieve the desired maximum emf is about 5.2 Hz, which corresponds to choice C.

Question 8

In a circuit made up of inductor L,resistance R,ammeter,battery and switch in series,the current is greatest at which of the following times,as measured after the switch is closed?

Accepted Answer

The current in an LR circuit is greatest after a long time has passed since the switch was closed, reaching its maximum value asymptotically. This is because the inductor initially opposes changes in current but eventually acts like a short circuit after a long time. Ten time constants (10τ) is a conventional time used to approximate when the current has reached its maximum steady-state value, as the circuit behaves almost like there's no inductor present.

Question 9

A circular loop (area = 0.20 m²)turns in a uniform magnetic field with B = 0.13 T.At an instant when the angle between the magnetic field and the normal to the plane of the loop is π rads and is decreasing at the rate of 0.50 rad/s,what is the magnitude of the emf induced in the loop?

Accepted Answer

The answer of A circular loop (area = 0.20 m²)turns...

Question 10

What is the self-inductance in a coil that experiences a 4.7-V induced emf when the current is changing at a rate of 200 A/s?

Accepted Answer

The answer of What is the self-inductance in a coil...

Question 11

By what factor is the self-inductance of an air solenoid changed if its length and number of coil turns both multiplied by eight?

Accepted Answer

The answer of By what factor is the self-inductance of...

Question 12

Two loops of wire are arranged so that a changing current in one,the primary,will induce a current in the other,the secondary.The secondary loop has twice as many turns as the primary loop.As long as the current in the primary is steady at 3 A,the current in the secondary will be:

Accepted Answer

A steady current in the primary loop does not change over time, so it does not induce any current in the secondary loop. Induction requires a changing magnetic field, which is not present with a steady current.

Question 13

A motor has an internal resistance of 13 Ω.When running,the motor has a back emf of 35 V and draws a current of 3.9 A.What is the supply voltage in this case?

Accepted Answer

The answer of A motor has an internal resistance of...

Question 14

An electric motor draws a current of 2.30 A from a 13.0-V battery when it runs at normal speed.If the motor's armature is "jammed" so that it cannot rotate,the current suddenly rises to 11.7 A.What is the back emf of the motor when running at normal speed?

Accepted Answer

When the motor is running at normal speed, the back emf is given by:

V - IaR = emf

where V is the battery voltage, Ia is the armature current, R is the resistance of the armature, and emf is the back emf.

Solving for emf, we get:

emf = V - IaR 
     = 13.0 V - 2.30 A × R

Now, when the armature is jammed and cannot rotate, the motor acts like a short circuit and the current is limited only by the resistance of the motor windings. In this case, the current is given by:

I = V / R

where I is the current, V is the battery voltage, and R is the total resistance of the motor windings.

Solving for R, we get:

R = V / I 
   = 13.0 V / 11.7 A 
   = 1.11 Ω

Now, we can use this value of R to find the back emf as follows:

emf = V - IaR 
     = 13.0 V - 2.30 A × 1.11 Ω 
     = 10.4 V

Therefore, the back emf of the motor when running at normal speed is 10.4 V, which is answer choice D.

Question 15

Electricity may be generated by rotating a loop of wire between the poles of a magnet.The induced current is greatest when:

Accepted Answer

The answer of Electricity may be generated by rotating a...

Question 16

A coil with a self-inductance of 0.80 mH experiences a constant current buildup from zero to 16 A in 0.50 s.What is the induced emf during this interval?

Accepted Answer

The answer of A coil with a self-inductance of 0.80...

Question 17

A coil is rotated in a magnetic field generating an emf given by emf = NBAω sin θ,where θ = ωt.At which angle θ is the emf one sixth of its maximum value?

Accepted Answer

The answer of A coil is rotated in a magnetic...

Question 18

Two loops of wire are arranged so that a changing current in one,the primary,will induce a current in the other,the secondary.The secondary loop has twice as many turns as the primary loop.The current in the primary at this moment is 3 A and increasing.The current in the secondary must be:

Accepted Answer

The question provides information about the number of turns in each loop and the current in the primary loop but does not specify the rate at which the current in the primary loop is changing (i.e., the rate of change of current or the magnetic flux), nor does it provide information about the resistance or other characteristics of the loops that would allow us to calculate the induced current in the secondary loop. Therefore, there is insufficient information to determine the induced current in the secondary loop.

Question 19

The current in a coil with a self-inductance of 2.3 mH increases from 0 to 1.9 A in a tenth of a second.What is the induced emf in the coil?

Accepted Answer

The induced emf (ε) can be calculated using the formula ε = -L * (ΔI/Δt), where L is the inductance (2.3 mH = 0.0023 H), ΔI is the change in current (1.9 A), and Δt is the change in time (0.1 s). Substituting these values gives ε = -0.0023 * (1.9/0.1) = -0.0437 V = -43.7 mV, which rounds to 44 mV.

Question 20

The self-inductance of a solenoid increases under which of the following conditions?

Accepted Answer

The self-inductance of a solenoid is directly proportional to the square of the number of turns of the coil. Therefore, increasing the number of coils would increase the self-inductance.

Quiz 20: Induced Voltages and Inductance

The "back emf" of a motor refers to a source of voltage that:

By what factor is the self-inductance of an air solenoid changed if only its cross-sectional area,A,multiplied by six?

A rectangular loop (area = 0.30 m²) turns in a uniform magnetic field with B = 0.50 T.At an instant when the angle between the magnetic field and the normal to the plane of the loop is π/2 rads and increasing at the rate of 0.52 rad/s,what is the magnitude of the emf induced in the loop?

By what factor is the self-inductance of an air solenoid changed if only its number of coil turns,N,is tripled?

When a voltage is generated by rotating a coil in a magnetic field at a constant rate,the period of the voltage equals the time that it takes for the coil to rotate through ________ radians.

In the United States,the value of ω for commercially generated power is ________ in SI units.

What is the minimum frequency with which a 200-turn,flat coil of cross sectional area 380 cm² can be rotated in a uniform 32-mT magnetic field if the maximum value of the induced emf is to equal 7.9 V?

In a circuit made up of inductor L,resistance R,ammeter,battery and switch in series,the current is greatest at which of the following times,as measured after the switch is closed?

A circular loop (area = 0.20 m²) turns in a uniform magnetic field with B = 0.13 T.At an instant when the angle between the magnetic field and the normal to the plane of the loop is π rads and is decreasing at the rate of 0.50 rad/s,what is the magnitude of the emf induced in the loop?

What is the self-inductance in a coil that experiences a 4.7-V induced emf when the current is changing at a rate of 200 A/s?

By what factor is the self-inductance of an air solenoid changed if its length and number of coil turns both multiplied by eight?

Two loops of wire are arranged so that a changing current in one,the primary,will induce a current in the other,the secondary.The secondary loop has twice as many turns as the primary loop.As long as the current in the primary is steady at 3 A,the current in the secondary will be:

A motor has an internal resistance of 13 Ω.When running,the motor has a back emf of 35 V and draws a current of 3.9 A.What is the supply voltage in this case?

An electric motor draws a current of 2.30 A from a 13.0-V battery when it runs at normal speed.If the motor's armature is "jammed" so that it cannot rotate,the current suddenly rises to 11.7 A.What is the back emf of the motor when running at normal speed?

Electricity may be generated by rotating a loop of wire between the poles of a magnet.The induced current is greatest when:

A coil with a self-inductance of 0.80 mH experiences a constant current buildup from zero to 16 A in 0.50 s.What is the induced emf during this interval?

A coil is rotated in a magnetic field generating an emf given by emf = NBAω sin θ,where θ = ωt.At which angle θ is the emf one sixth of its maximum value?

Two loops of wire are arranged so that a changing current in one,the primary,will induce a current in the other,the secondary.The secondary loop has twice as many turns as the primary loop.The current in the primary at this moment is 3 A and increasing.The current in the secondary must be:

The current in a coil with a self-inductance of 2.3 mH increases from 0 to 1.9 A in a tenth of a second.What is the induced emf in the coil?

The self-inductance of a solenoid increases under which of the following conditions?

Quiz 20: Induced Voltages and Inductance

The "back emf" of a motor refers to a source of voltage that:

By what factor is the self-inductance of an air solenoid changed if only its cross-sectional area,A,multiplied by six?

A rectangular loop (area = 0.30 m2) turns in a uniform magnetic field with B = 0.50 T.At an instant when the angle between the magnetic field and the normal to the plane of the loop is π/2 rads and increasing at the rate of 0.52 rad/s,what is the magnitude of the emf induced in the loop?

By what factor is the self-inductance of an air solenoid changed if only its number of coil turns,N,is tripled?

When a voltage is generated by rotating a coil in a magnetic field at a constant rate,the period of the voltage equals the time that it takes for the coil to rotate through ________ radians.

In the United States,the value of ω for commercially generated power is ________ in SI units.

What is the minimum frequency with which a 200-turn,flat coil of cross sectional area 380 cm2 can be rotated in a uniform 32-mT magnetic field if the maximum value of the induced emf is to equal 7.9 V?

In a circuit made up of inductor L,resistance R,ammeter,battery and switch in series,the current is greatest at which of the following times,as measured after the switch is closed?

A circular loop (area = 0.20 m2) turns in a uniform magnetic field with B = 0.13 T.At an instant when the angle between the magnetic field and the normal to the plane of the loop is π rads and is decreasing at the rate of 0.50 rad/s,what is the magnitude of the emf induced in the loop?

What is the self-inductance in a coil that experiences a 4.7-V induced emf when the current is changing at a rate of 200 A/s?

By what factor is the self-inductance of an air solenoid changed if its length and number of coil turns both multiplied by eight?

Two loops of wire are arranged so that a changing current in one,the primary,will induce a current in the other,the secondary.The secondary loop has twice as many turns as the primary loop.As long as the current in the primary is steady at 3 A,the current in the secondary will be:

A motor has an internal resistance of 13 Ω.When running,the motor has a back emf of 35 V and draws a current of 3.9 A.What is the supply voltage in this case?

An electric motor draws a current of 2.30 A from a 13.0-V battery when it runs at normal speed.If the motor's armature is "jammed" so that it cannot rotate,the current suddenly rises to 11.7 A.What is the back emf of the motor when running at normal speed?

Electricity may be generated by rotating a loop of wire between the poles of a magnet.The induced current is greatest when:

A coil with a self-inductance of 0.80 mH experiences a constant current buildup from zero to 16 A in 0.50 s.What is the induced emf during this interval?

A coil is rotated in a magnetic field generating an emf given by emf = NBAω sin θ,where θ = ωt.At which angle θ is the emf one sixth of its maximum value?

Two loops of wire are arranged so that a changing current in one,the primary,will induce a current in the other,the secondary.The secondary loop has twice as many turns as the primary loop.The current in the primary at this moment is 3 A and increasing.The current in the secondary must be:

The current in a coil with a self-inductance of 2.3 mH increases from 0 to 1.9 A in a tenth of a second.What is the induced emf in the coil?

The self-inductance of a solenoid increases under which of the following conditions?

A rectangular loop (area = 0.30 m²) turns in a uniform magnetic field with B = 0.50 T.At an instant when the angle between the magnetic field and the normal to the plane of the loop is π/2 rads and increasing at the rate of 0.52 rad/s,what is the magnitude of the emf induced in the loop?

What is the minimum frequency with which a 200-turn,flat coil of cross sectional area 380 cm² can be rotated in a uniform 32-mT magnetic field if the maximum value of the induced emf is to equal 7.9 V?

A circular loop (area = 0.20 m²) turns in a uniform magnetic field with B = 0.13 T.At an instant when the angle between the magnetic field and the normal to the plane of the loop is π rads and is decreasing at the rate of 0.50 rad/s,what is the magnitude of the emf induced in the loop?