Question 1

In the figure, a bar magnet moves away from the solenoid. The direction of the induced current through the resistor R is

Accepted Answer

A)  from a to b. 
B)  from b to a. 
C)  No current is induced. 
A)  from a to b. 
B)  from b to a. 
C)  No current is induced.

Question 2

A sinusoidal electromagnetic wave has a peak electric field of $8.00 \mathrm { kV } / \mathrm { m }$ What is the intensity of the wave? $\left( c = 3.0 \times 10 ^ { 8 } \mathrm {~m} / \mathrm { s } \right.$ $\mu _ { 0 } = 4 \pi \times 10 ^ { - 7 } \mathrm {~T} \cdot \mathrm { m } / \mathrm { A } ,$ $\left. \varepsilon _ { 0 } = 8.85 \times 10 ^ { - 12 } \mathrm { C } ^ { 2 } / \mathrm { N } \cdot \mathrm { m } ^ { 2 } \right)$

Accepted Answer

A)  170 kW/m2 
B)  85 kW/m2 
C)  21 kW/m2 
D)  11 kW/m2 
A)  170 kW/m2 
B)  85 kW/m2 
C)  21 kW/m2 
D)  11 kW/m2

Question 3

A light source radiates 60.0 W of single-wavelength sinusoidal light uniformly in all directions. What is the average intensity of the light from this bulb at a distance of 0.400 m from the bulb?

Accepted Answer

A)  14.9 W/m2 
B)  37.2 W/m2 
C)  27.4 W/m2 
D)  11.9 W/m2 
E)  29.8 W/m2 
A)  14.9 W/m2 
B)  37.2 W/m2 
C)  27.4 W/m2 
D)  11.9 W/m2 
E)  29.8 W/m2

Question 4

A flat circular loop having one turn and radius 5.0 cm is positioned with its plane perpendicular to a uniform 0.60-T magnetic field. The area of the loop is suddenly reduced to essentially zero in 0.50 ms. What emf is induced in the loop?

Accepted Answer

The answer of A flat circular loop having one turn...

Question 5

A conducting rod whose length is ℓ = 27.0 cm is placed on frictionless U-shaped metal rails that is connected to a lightbulb having a resistance of 5.00 Ω as shown in the figure. The rails and the rod are in the plane of the page. A constant uniform magnetic field of strength 1.20 T is applied perpendicular to and out of the paper. An external applied force moves the rod to the right with a constant speed. At what speed should the rod be pulled so that the lightbulb will consume energy at a rate of 1.10 W?

Accepted Answer

A)  2.00 m/s 
B)  3.50 m/s 
C)  4.26 m/s 
D)  6.00 m/s 
E)  7.24 m/s 
A)  2.00 m/s 
B)  3.50 m/s 
C)  4.26 m/s 
D)  6.00 m/s 
E)  7.24 m/s

Question 6

A circular conducting loop with a radius of $0.50 \mathrm {~m}$ and a small gap filled with a $10.0 - \Omega$ resistor is oriented in the $x y - p l a n e .$ If a uniform magnetic field of $1.0 \mathrm {~T}$ making an angle of $30 ^ { \circ }$ with the $\text { z-axis, }$ increases to $10.0 \mathrm {~T} ,$ in $4.0 \mathrm {~s} ,$ what is the magnitude of the current that will be caused to flow in the loop if it has negligible resistance?

Accepted Answer

A)  0.01530393 A 
B)  0.08835729 A 
C)  0.15303932 A 
D)  0 A 
A)  0.01530393 A 
B)  0.08835729 A 
C)  0.15303932 A 
D)  0 A

Question 7

A conducting rod whose length is ℓ = 1.60 m is placed on frictionless U-shaped metal rails that is connected to a lightbulb having a resistance of 4.00 Ω as shown in the figure. The rails and the rod are in the plane of the page. A constant uniform magnetic field of strength 2.20 T is applied perpendicular to and out of the paper. What is the magnitude of the external applied force needed to move the rod to the right with a constant speed of 6.00 m/s?

Accepted Answer

A)  8.60 N 
B)  9.30 N 
C)  10.6 N 
D)  12.6 N 
E)  18.6 N 
A)  8.60 N 
B)  9.30 N 
C)  10.6 N 
D)  12.6 N 
E)  18.6 N

Question 8

A coil lies flat on a level tabletop in a region where the magnetic field vector points straight up. The magnetic field suddenly grows stronger. When viewed from above, what is the direction of the induced current in this coil as the field increases?

Accepted Answer

A)  counterclockwise 
B)  clockwise 
C)  clockwise initially, then counterclockwise before stopping 
D)  There is no induced current in this coil. 
A)  counterclockwise 
B)  clockwise 
C)  clockwise initially, then counterclockwise before stopping 
D)  There is no induced current in this coil.

Question 9

What is the maximum value of the magnetic field at a distance of 2.5 m from a light bulb that radiates 100 W of single-frequency sinusoidal electromagnetic waves uniformly in all directions? (ε0 = 8.85 × 10-12 C2/N ∙ m2, μ0 = 4π × 10-7 T ∙ m/A, c = 3.0 × 108 m/s)

Accepted Answer

A)  0.10 μT 
B)  0.40 μT 
C)  0.50 μT 
D)  0.60 μT 
E)  0.80 μT 
A)  0.10 μT 
B)  0.40 μT 
C)  0.50 μT 
D)  0.60 μT 
E)  0.80 μT

Question 10

What is the wavelength of the most intense light emitted by a giant star of surface temperature 5000 K? The constant in Wien's law is 0.00290 m ∙ K.

Accepted Answer

A)  576 nm 
B)  578 nm 
C)  580 nm 
D)  582 nm 
A)  576 nm 
B)  578 nm 
C)  580 nm 
D)  582 nm

Question 11

An eagle, with a wingspread of 2.0 m, flies toward the north at 8.0 m/s in a region where the vertical component of the earth's magnetic field is 0.20 × 10-4 T. What emf would be developed between the eagle's wing tips? (It has been speculated that this phenomenon could play a role in the navigation of birds, but the effect is too small, in all likelihood.)

Accepted Answer

Question 12

If unpolarized light of intensity I0 passes through an ideal polarizer, what is the intensity of the emerging light?

Accepted Answer

A)  I0 
B)  I0/2 
C)  I0/4 
D)  I0/ $\sqrt { 2 }$ 
E)  I0/16 
A)  I0 
B)  I0/2 
C)  I0/4 
D)  I0/ $\sqrt { 2 }$ 
E)  I0/16

Question 13

The maximum value of the electric field in an electromagnetic wave is 2.0 V/m. What is the maximum value of the magnetic field in that wave? (c = 3.0 × 108 m/s)

Accepted Answer

A)  6.7 pT 
B)  6.7 mT 
C)  6.7 nT 
D)  6.7 μT 
E)  6.7 T 
A)  6.7 pT 
B)  6.7 mT 
C)  6.7 nT 
D)  6.7 μT 
E)  6.7 T

Question 14

A bar magnet is close to a solenoid, as shown in the figure. As viewed through the solenoid looking toward the magnet, what is the direction (clockwise or counterclockwise) of the current (if any) induced in the solenoid in each case?
(a) The magnet is pushed toward the solenoid.
(b) The magnet and solenoid both move to the right at 25 cm/s.

Accepted Answer

(a) counte

Question 15

A flat coil is in a uniform magnetic field. The magnetic flux through the coil is greatest when the plane of its area is

Accepted Answer

A)  parallel to the magnetic field. 
B)  at 45° with the magnetic field. 
C)  perpendicular to the magnetic field. 
A)  parallel to the magnetic field. 
B)  at 45° with the magnetic field. 
C)  perpendicular to the magnetic field.

Question 16

What frequency of electromagnetic radiation has photons of energy 4.7 × 10-25 J? (h = 6.626 × 10-34 J ∙ s)

Accepted Answer

A)  710 kHz 
B)  4.7 MHz 
C)  710 MHz 
D)  1.4 GHz 
A)  710 kHz 
B)  4.7 MHz 
C)  710 MHz 
D)  1.4 GHz

Question 17

The cosmic background radiation permeating the universe has the spectrum of a 2.7-K blackbody radiator. What is the peak wavelength of this radiation? The constant in Wien's law is 0.0029 m ∙ K.

Accepted Answer

1.1 mm (mi

Question 18

A 7.55 × $10^{14}$ Hz electromagnetic wave travels in carbon tetrachloride with a speed of 2.05 ×108 m/s. What is the wavelength of the wave in this material?

Accepted Answer

A)  272 nm 
B)  301 nm 
C)  338 nm 
D)  361 nm 
E)  397 nm 
A)  272 nm 
B)  301 nm 
C)  338 nm 
D)  361 nm 
E)  397 nm

Question 19

A conducting rod whose length is ℓ = 25 cm is placed on a U-shaped metal wire that is connected to a lightbulb having a resistance of 8.0 Ω as shown in the figure. The wire and the rod are in the plane of the page. A constant uniform magnetic field of strength 0.40 T is applied perpendicular to and out of the paper. An external applied force moves the rod to the left with a constant speed of 12 m/s. What are the magnitude and direction of the induced current in the circuit?

Accepted Answer

A)  150 mA clockwise 
B)  150 mA counterclockwise 
C)  34 mA counterclockwise 
D)  34 mA clockwise 
E)  100 mA clockwise 
A)  150 mA clockwise 
B)  150 mA counterclockwise 
C)  34 mA counterclockwise 
D)  34 mA clockwise 
E)  100 mA clockwise

Question 20

The following items are positioned in sequence: A source of a beam of natural light of intensity I0, three ideal polarizers A, B, and C; and an observer. Polarizer axis angles are measured clockwise from the vertical, as viewed by the observer. The axis angle of polarizer A is set at 0° (vertical), and the axis angle of polarizer C is set at 50°. Polarizer B is set so that the beam intensity is zero at the observer. What are the two possible axis angle settings (less than 180°) of polarizer B?

Accepted Answer

A)  40° and 90° 
B)  40° and 130° 
C)  40° and 140° 
D)  90° and 130° 
E)  90° and 140° 
A)  40° and 90° 
B)  40° and 130° 
C)  40° and 140° 
D)  90° and 130° 
E)  90° and 140°

Exam 25: EM Induction and Em Waves

In the figure, a bar magnet moves away from the solenoid. The direction of the induced current through the resistor R is

A light source radiates 60.0 W of single-wavelength sinusoidal light uniformly in all directions. What is the average intensity of the light from this bulb at a distance of 0.400 m from the bulb?

A flat circular loop having one turn and radius 5.0 cm is positioned with its plane perpendicular to a uniform 0.60-T magnetic field. The area of the loop is suddenly reduced to essentially zero in 0.50 ms. What emf is induced in the loop?

A coil lies flat on a level tabletop in a region where the magnetic field vector points straight up. The magnetic field suddenly grows stronger. When viewed from above, what is the direction of the induced current in this coil as the field increases?

What is the maximum value of the magnetic field at a distance of 2.5 m from a light bulb that radiates 100 W of single-frequency sinusoidal electromagnetic waves uniformly in all directions? (ε0 = 8.85 × 10-12 C2/N ∙ m2, μ0 = 4π × 10-7 T ∙ m/A, c = 3.0 × 108 m/s)

What is the wavelength of the most intense light emitted by a giant star of surface temperature 5000 K? The constant in Wien's law is 0.00290 m ∙ K.

If unpolarized light of intensity I0 passes through an ideal polarizer, what is the intensity of the emerging light?

The maximum value of the electric field in an electromagnetic wave is 2.0 V/m. What is the maximum value of the magnetic field in that wave? (c = 3.0 × 108 m/s)

A flat coil is in a uniform magnetic field. The magnetic flux through the coil is greatest when the plane of its area is

What frequency of electromagnetic radiation has photons of energy 4.7 × 10-25 J? (h = 6.626 × 10-34 J ∙ s)

The cosmic background radiation permeating the universe has the spectrum of a 2.7-K blackbody radiator. What is the peak wavelength of this radiation? The constant in Wien's law is 0.0029 m ∙ K.

A 7.55 × 101410^{14}1014 Hz electromagnetic wave travels in carbon tetrachloride with a speed of 2.05 ×108 m/s. What is the wavelength of the wave in this material?

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What is the maximum value of the magnetic field at a distance of 2.5 m from a light bulb that radiates 100 W of single-frequency sinusoidal electromagnetic waves uniformly in all directions? (ε₀ = 8.85 × 10^-12 C²/N ∙ m², μ₀ = 4π × 10^-7 T ∙ m/A, c = 3.0 × 10⁸ m/s)

If unpolarized light of intensity I₀ passes through an ideal polarizer, what is the intensity of the emerging light?

The maximum value of the electric field in an electromagnetic wave is 2.0 V/m. What is the maximum value of the magnetic field in that wave? (c = 3.0 × 10⁸ m/s)

What frequency of electromagnetic radiation has photons of energy 4.7 × 10^-25 J? (h = 6.626 × 10^-34 J ∙ s)

A 7.55 × $10^{14}$ Hz electromagnetic wave travels in carbon tetrachloride with a speed of 2.05 ×10⁸ m/s. What is the wavelength of the wave in this material?