Question 1

FIGURE 29-13 
-The windings of a motor have a resistance of 4.0 Ω. The counter emf of this motor when connected to a 120-V line and running at full speed is 104 V.
(a) What is the start up current of this motor?
(b) What is the current in the motor when running at full speed?

Accepted Answer

The answer of FIGURE 29-13 
-The windings of a motor...

Question 2

A circular loop of radius 0.10 m is rotating in a uniform magnetic field of 0.20 T. Find the magnetic flux through the loop when the plane of the loop and the magnetic field vector are parallel.

Accepted Answer

The answer of A circular loop of radius 0.10 m...

Question 3

FIGURE 29-12 
-A conducting rod whose length is 25 cm is placed on a U-shaped metal wire that has a resistance R of 8 Ω as shown in Fig. 29-12. The wire and the rod are in the plane of the paper. A constant magnetic field of strength 0.4 T is applied perpendicular and into the paper. An applied force moves the rod to the right with a constant speed of 6 m/s.
(a) What is the magnitude of the induced emf in the wire?
(b) What is the magnitude and direction of the induced current in the wire?

Accepted Answer

The answer of FIGURE 29-12 
-A conducting rod whose length...

Question 4

A conducting loop in the form of a circle is placed perpendicular to a magnetic field of 0.50 T. If the area of the loop decreases at a rate of 3.0 × 10^-3 m² /s, what is the induced emf in the loop?

Accepted Answer

The answer of A conducting loop in the form of...

Question 5

A square coil of wire with 15 turns and an area of 0.40 m² is placed parallel to a magnetic field of 0.75 T. The coil is flipped so its plane is perpendicular to the magnetic field in 0.050 s. What is the magnitude of the average induced emf?

Accepted Answer

The answer of A square coil of wire with 15...

Question 6

FIGURE 29-13 
-A DC motor of internal resistance 6.0 Ω is connected to a 24-V power supply. The operating current is 1.0 A.
(a) What is the start-up current?
(b) What is the back emf when the motor is running at full speed?
(c) What is the back emf when the motor is running at half speed?

Accepted Answer

The answer of FIGURE 29-13 
-A DC motor of internal...

Question 7

A loop of radius r = 3 cm is placed parallel to the xy-plane in a uniform magnetic field  = ( 0.75 T)  . The resistance of the loop is R = 18 Ω. Starting at t = 0, the magnitude of the field decreases uniformly to B = 0 in 0.15 seconds. What is the magnitude of the electric current produced in the loop during that time?

Accepted Answer

The answer of A loop of radius r = 3...

Question 8

A 20-turn coil of area 0.32 m² is placed in a uniform magnetic field of 0.055 T so that the perpendicular to the plane of the coil makes an angle of 30° with respect to the magnetic field. The flux through the coil is

Accepted Answer

The answer of A 20-turn coil of area 0.32 m²...

Question 9

A ten loop coil of area 0.23 m² is in a 0.047 T uniform magnetic field oriented so that the maximum flux goes through the coil. The average emf induced in the coil is

Accepted Answer

The answer of A ten loop coil of area 0.23...

Question 10

FIGURE 29-13 
-A power transmission line 50 km long has a total resistance of 0.60 Ω. A generator produces 100 V at 70 A. In order to reduce energy loss due to heating of the transmission line, the voltage is stepped up with a transformer with a turns ratio of 100:1.
(a) What percentage of the original energy would be lost if the transformer were not used?
(b) What percentage of the original energy is lost when the transformer is used?

Accepted Answer

The answer of FIGURE 29-13 
-A power transmission line 50...

Question 11

A ten loop coil of area 0.23 m² is in a 0.047 T uniform magnetic field oriented so that the maximum flux goes through the coil. The coil is then rotated so that the flux through it goes to zero in 0.34 s. The average emf induced in the coil during the 0.34 s is

Accepted Answer

The answer of A ten loop coil of area 0.23...

Question 12

A constant magnetic field of 0.50 T is applied to a rectangular loop of area 3.0 × 10^-3 m². If the area of this loop changes from its original value to a new value of 1.6 × 10^-3 m² in 1.6 s, what is the emf induced in the loop?

Accepted Answer

The answer of A constant magnetic field of 0.50 T...

Question 13

A ten loop coil of area 0.23 m² is in a 0.047 T uniform magnetic field oriented so that the maximum flux goes through the coil. This flux is

Accepted Answer

The answer of A ten loop coil of area 0.23...

Question 14

A circular loop of radius 0.10 m is rotating in a uniform magnetic field of 0.20 T. Find the magnetic flux through the loop when the plane of the loop and the magnetic field vector are perpendicular.

Accepted Answer

The answer of A circular loop of radius 0.10 m...

Question 15

A circular loop of radius 0.10 m is rotating in a uniform magnetic field of 0.20 T. Find the magnetic flux through the loop when the plane of the loop and the magnetic field vector are at an angle of 30°.

Accepted Answer

The magnetic flux Φ through the loop is given by Φ = B * A * cos(θ), where B is the magnetic field (0.20 T), A is the area of the loop (π * (0.10 m)^2), and θ is the angle between the magnetic field and the normal to the plane of the loop (30°). Calculating this gives Φ = 0.20 * π * (0.10)^2 * cos(30°) = 3.1 × 10^-3 T∙m^2.

Question 16

FIGURE 29-13 
-A conducting bar moves along frictionless conducting rails connected to a 4.00-Ω resistor as shown in Fig. 29-13. The length of the bar is 1.60 m and a uniform magnetic field of 2.20 T is applied perpendicular to the paper.
(a) What is the applied force required to move the bar to the right with a constant speed of 6.00 m/s?
(b) At what rate is energy dissipated in the 4.00 Ω resistor?

Accepted Answer

The answer of FIGURE 29-13 
-A conducting bar moves along...

Question 17

A uniform magnetic field is applied perpendicular to the plane of a 60-turn circular coil with a radius of 6.0 cm and a resistance of 0.60 Ω. If the magnetic field increases from 0.20 T to 1.8 T in 0.20 s, what is the emf induced in that coil?

Accepted Answer

The answer of A uniform magnetic field is applied perpendicular...

Question 18

A conducting loop in the form of a circle is placed perpendicular to a magnetic field of 0.50 T. If the area of the loop increases at a rate of 3.0 × 10^-3 m² /s, what is the induced emf in the loop?

Accepted Answer

The answer of A conducting loop in the form of...

Question 19

The flux through a coil changes from 4.0 × 10^-⁵ Wb to 5.0 × 10^-⁵ Wb in 0.10 s. What emf is induced in this coil?

Accepted Answer

The induced emf (ε) can be calculated using Faraday's law of electromagnetic induction: ε = -ΔΦ/Δt. Here, ΔΦ = 5.0 × 10^-5 Wb - 4.0 × 10^-5 Wb = 1.0 × 10^-5 Wb and Δt = 0.10 s. Thus, ε = -(1.0 × 10^-5 Wb) / 0.10 s = -1.0 × 10^-4 V. The negative sign indicates the direction of the induced emf, but the magnitude is 1.0 × 10^-4 V.

Question 20

The area of a rectangular loop of wire is 3.6 × 10^-3 m². The loop is placed in a magnetic field that changes from 0.20 T to 1.4 T in 1.6 s. The plane of the loop is perpendicular to the direction of the magnetic field. What is the magnitude of the induced emf in that loop?

Accepted Answer

The induced emf can be found using Faraday's law of electromagnetic induction:
emf = -N*d(phi)/dt
where N is the number of turns in the loop, and d(phi)/dt is the rate of change of magnetic flux through the loop. Since the magnetic field is changing, there is a changing magnetic flux through the loop given by:
phi = B*A*cos(theta)
where A is the area of the loop, B is the magnitude of the magnetic field, and theta is the angle between the normal to the loop and the magnetic field. In this case, theta is 90 degrees since the plane of the loop is perpendicular to the magnetic field. Thus, the changing magnetic flux is given by:
d(phi)/dt = A*cos(theta)*dB/dt = 3.6 × 10^-3*1*(-0.875)/1.6 = -1.575 × 10^-3 Wb/s
where dB/dt is the rate of change of the magnetic field, which is -0.875 T/s. Plugging in the numbers, we get:
emf = -N*d(phi)/dt = -1*(-1.575 × 10^-3) = 1.575 × 10^-3 V
which is approximately equal to 2.7 × 10^-3 V in scientific notation. Therefore, the best choice is B.

Quiz 29: Electromagnetic Induction and Faradays Law

FIGURE 29-13 -The windings of a motor have a resistance of 4.0 Ω. The counter emf of this motor when connected to a 120-V line and running at full speed is 104 V. (a) What is the start up current of this motor? (b) What is the current in the motor when running at full speed?

A circular loop of radius 0.10 m is rotating in a uniform magnetic field of 0.20 T. Find the magnetic flux through the loop when the plane of the loop and the magnetic field vector are parallel.

A conducting loop in the form of a circle is placed perpendicular to a magnetic field of 0.50 T. If the area of the loop decreases at a rate of 3.0 × 10-3 m2 /s, what is the induced emf in the loop?

A square coil of wire with 15 turns and an area of 0.40 m2 is placed parallel to a magnetic field of 0.75 T. The coil is flipped so its plane is perpendicular to the magnetic field in 0.050 s. What is the magnitude of the average induced emf?

FIGURE 29-13 -A DC motor of internal resistance 6.0 Ω is connected to a 24-V power supply. The operating current is 1.0 A. (a) What is the start-up current? (b) What is the back emf when the motor is running at full speed? (c) What is the back emf when the motor is running at half speed?

A 20-turn coil of area 0.32 m2 is placed in a uniform magnetic field of 0.055 T so that the perpendicular to the plane of the coil makes an angle of 30° with respect to the magnetic field. The flux through the coil is

A ten loop coil of area 0.23 m2 is in a 0.047 T uniform magnetic field oriented so that the maximum flux goes through the coil. The average emf induced in the coil is

A ten loop coil of area 0.23 m2 is in a 0.047 T uniform magnetic field oriented so that the maximum flux goes through the coil. The coil is then rotated so that the flux through it goes to zero in 0.34 s. The average emf induced in the coil during the 0.34 s is

A constant magnetic field of 0.50 T is applied to a rectangular loop of area 3.0 × 10-3 m2. If the area of this loop changes from its original value to a new value of 1.6 × 10-3 m2 in 1.6 s, what is the emf induced in the loop?

A ten loop coil of area 0.23 m2 is in a 0.047 T uniform magnetic field oriented so that the maximum flux goes through the coil. This flux is

A circular loop of radius 0.10 m is rotating in a uniform magnetic field of 0.20 T. Find the magnetic flux through the loop when the plane of the loop and the magnetic field vector are perpendicular.

A circular loop of radius 0.10 m is rotating in a uniform magnetic field of 0.20 T. Find the magnetic flux through the loop when the plane of the loop and the magnetic field vector are at an angle of 30°.

A uniform magnetic field is applied perpendicular to the plane of a 60-turn circular coil with a radius of 6.0 cm and a resistance of 0.60 Ω. If the magnetic field increases from 0.20 T to 1.8 T in 0.20 s, what is the emf induced in that coil?

A conducting loop in the form of a circle is placed perpendicular to a magnetic field of 0.50 T. If the area of the loop increases at a rate of 3.0 × 10-3 m2 /s, what is the induced emf in the loop?

The flux through a coil changes from 4.0 × 10-5 Wb to 5.0 × 10-5 Wb in 0.10 s. What emf is induced in this coil?

The area of a rectangular loop of wire is 3.6 × 10-3 m2. The loop is placed in a magnetic field that changes from 0.20 T to 1.4 T in 1.6 s. The plane of the loop is perpendicular to the direction of the magnetic field. What is the magnitude of the induced emf in that loop?

A conducting loop in the form of a circle is placed perpendicular to a magnetic field of 0.50 T. If the area of the loop decreases at a rate of 3.0 × 10^-3 m² /s, what is the induced emf in the loop?

A square coil of wire with 15 turns and an area of 0.40 m² is placed parallel to a magnetic field of 0.75 T. The coil is flipped so its plane is perpendicular to the magnetic field in 0.050 s. What is the magnitude of the average induced emf?

A 20-turn coil of area 0.32 m² is placed in a uniform magnetic field of 0.055 T so that the perpendicular to the plane of the coil makes an angle of 30° with respect to the magnetic field. The flux through the coil is

A ten loop coil of area 0.23 m² is in a 0.047 T uniform magnetic field oriented so that the maximum flux goes through the coil. The average emf induced in the coil is

A ten loop coil of area 0.23 m² is in a 0.047 T uniform magnetic field oriented so that the maximum flux goes through the coil. The coil is then rotated so that the flux through it goes to zero in 0.34 s. The average emf induced in the coil during the 0.34 s is

A constant magnetic field of 0.50 T is applied to a rectangular loop of area 3.0 × 10^-3 m². If the area of this loop changes from its original value to a new value of 1.6 × 10^-3 m² in 1.6 s, what is the emf induced in the loop?

A ten loop coil of area 0.23 m² is in a 0.047 T uniform magnetic field oriented so that the maximum flux goes through the coil. This flux is

A conducting loop in the form of a circle is placed perpendicular to a magnetic field of 0.50 T. If the area of the loop increases at a rate of 3.0 × 10^-3 m² /s, what is the induced emf in the loop?

The flux through a coil changes from 4.0 × 10^-⁵ Wb to 5.0 × 10^-⁵ Wb in 0.10 s. What emf is induced in this coil?

The area of a rectangular loop of wire is 3.6 × 10^-3 m². The loop is placed in a magnetic field that changes from 0.20 T to 1.4 T in 1.6 s. The plane of the loop is perpendicular to the direction of the magnetic field. What is the magnitude of the induced emf in that loop?