Question 1

By what primary heat transfer mechanism does the sun warm the earth?

Accepted Answer

A)  convection 
B)  conduction 
C)  radiation 
D)  All of the above processes are equally important in combination. 
A)  convection 
B)  conduction 
C)  radiation 
D)  All of the above processes are equally important in combination.

Question 2

How far does a beam of light travel in 2.0 ms? (c = 3.0 × 108 m/s)

Accepted Answer

A)  6.0 × 105 m 
B)  0.66 × 105 m 
C)  90 m 
D)  70 m 
E)  60 m 
A)  6.0 × 105 m 
B)  0.66 × 105 m 
C)  90 m 
D)  70 m 
E)  60 m

Question 3

What is the wavelength used by a radio station that broadcasts at a frequency of 920 kHz? (c = 3.00 × 108 m/s)

Accepted Answer

A)  22.6 m 
B)  226 m 
C)  326 m 
D)  175 m 
E)  276 m 
A)  22.6 m 
B)  226 m 
C)  326 m 
D)  175 m 
E)  276 m

Question 4

A giant star radiates energy at the rate of 3.0 × 1030 W, and its surface temperature has been measured to be 3000 K. Assuming that it is a perfect emitter, what is the radius of this star?(σ = 5.67 × 10-8 W/m2 ∙ K4)

Accepted Answer

A)  7.8 × 1010 m 
B)  8.7 × 1010 m 
C)  1.4 × 1010 m 
D)  1.9 × 1011 m 
E)  2.3 × 1011 m 
A)  7.8 × 1010 m 
B)  8.7 × 1010 m 
C)  1.4 × 1010 m 
D)  1.9 × 1011 m 
E)  2.3 × 1011 m

Question 5

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 at the observer is a maximum. What is the axis angle settings of polarizer B?

Accepted Answer

A)  0° 
B)  25° 
C)  50° 
D)  75° 
E)  100° 
A)  0° 
B)  25° 
C)  50° 
D)  75° 
E)  100°

Question 6

A airplane having a metal surface and a wingspan of 25.0 m flies horizontally at 200. m/s where the earth's magnetic field is vertical with magnitude 45.0 μT.
(a) What emf is induced across the wings?
(b) What wingspan would the plane need to produce 1.00-V emf across its wings?
(c) The plane now reverses direction. Does the polarity of the wingtip emf change? That is, if the left wing was positive before, does it now become negative?

Accepted Answer

(a) 0.225

Question 7

What is the surface temperature of a star, if its radiation peak occurs at a frequency of 1.06 × 1015 Hz? (c = 3.00 × 108 m/s, and the constant in Wien's law is 0.00290 m ∙ K)

Accepted Answer

A)  17,000 K 
B)  14,500 K 
C)  19,000 K 
D)  20,400 K 
E)  10,200 K 
A)  17,000 K 
B)  14,500 K 
C)  19,000 K 
D)  20,400 K 
E)  10,200 K

Question 8

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. An external applied force moves the rod to the right with a constant speed of 6.00 m/s. At what rate is energy dissipated in the lightbulb?

Accepted Answer

A)  60.0 W 
B)  121 W 
C)  21.2 W 
D)  112 W 
E)  11.5 W 
A)  60.0 W 
B)  121 W 
C)  21.2 W 
D)  112 W 
E)  11.5 W

Question 9

As shown in the figure, a metal bar is in contact with a pair of parallel rails and is in motion with an upward velocity of magnitude ν. A uniform magnetic field is present, directed downward as shown. 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 10

About 1350 W/m2 of electromagnetic energy reaches the upper atmosphere of the earth from the sun, which is 1.5 × 1011 m away. Use this information to estimate the average power output of the sun.

Accepted Answer

A)  1 × 1026 W 
B)  2 × 1026 W 
C)  3 × 1026 W 
D)  4 × 1026 W 
A)  1 × 1026 W 
B)  2 × 1026 W 
C)  3 × 1026 W 
D)  4 × 1026 W

Question 11

A radiometer has two square vanes (1.0 cm by 1.0 cm), attached to a light horizontal cross arm, and pivoted about a vertical axis through the center, as shown in the figure. The center of each vane is 6.0 cm from the axis. One vane is silvered and it reflects all radiant energy that falls upon it. The other vane is blackened and it absorbs all incident radiant energy. Radiant energy, having an intensity of 300 W/m2, is incident normally upon the front surfaces of both vanes. What is the radiant power absorbed by the blackened vane?

Accepted Answer

A)  0.030 W 
B)  0.040 W 
C)  0.050 W 
D)  0.060 W 
E)  0.090 W 
A)  0.030 W 
B)  0.040 W 
C)  0.050 W 
D)  0.060 W 
E)  0.090 W

Question 12

A conducting rod with a length 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 into the paper. An external applied force moves the rod to the right with a constant speed of 6.0 m/s. What are the magnitude and direction of the induced current in the circuit?

Accepted Answer

A)  17 mA clockwise 
B)  17 mA counterclockwise 
C)  75 mA counterclockwise 
D)  75 mA clockwise 
E)  52 mA clockwise 
A)  17 mA clockwise 
B)  17 mA counterclockwise 
C)  75 mA counterclockwise 
D)  75 mA clockwise 
E)  52 mA clockwise

Question 13

A bar magnet is oriented above a copper ring, as shown in the figure. If the magnet is kept fixed while the ring is dropped, what is the direction of the current induced in the ring, as viewed from below the ring?

Accepted Answer

A)  There is no current in the ring. 
B)  counterclockwise 
C)  clockwise 
A)  There is no current in the ring. 
B)  counterclockwise 
C)  clockwise

Question 14

In an electromagnetic wave in free space, the electric and magnetic fields are

Accepted Answer

A)  parallel to one another and perpendicular to the direction of wave propagation. 
B)  parallel to one another and parallel to the direction of wave propagation. 
C)  perpendicular to one another and perpendicular to the direction of wave propagation. 
D)  perpendicular to one another and parallel to the direction of wave propagation. 
A)  parallel to one another and perpendicular to the direction of wave propagation. 
B)  parallel to one another and parallel to the direction of wave propagation. 
C)  perpendicular to one another and perpendicular to the direction of wave propagation. 
D)  perpendicular to one another and parallel to the direction of wave propagation.

Question 15

An 800-kHz sinusoidal radio signal is detected at a point 2.1 km distant from a transmitter tower. The electric field amplitude of the signal at that point is 0.80 V/m. Assume that the signal power is radiated uniformly in all directions and that radio waves incident upon the ground are completely absorbed. What is the intensity of the radio signal at that point? (ε0 = 8.85 × 10-12 C2/N ∙ m2, μ0 = 4π × 10-7 T ∙ m/A, c = 3.0 × 108 m/s)

Accepted Answer

A)  8.5 × 10-4 W/m2 
B)  1.2 × 10-3 W/m2 
C)  1.7 × 10-3 W/m2 
D)  6.0 × 10-4 W/m2 
E)  4.2 × 10-4 W/m2 
A)  8.5 × 10-4 W/m2 
B)  1.2 × 10-3 W/m2 
C)  1.7 × 10-3 W/m2 
D)  6.0 × 10-4 W/m2 
E)  4.2 × 10-4 W/m2

Question 16

A long vertical wire carries a steady 70 A current. As shown in the figure, a pair of horizontal rails are 0.20 m apart. A 20-Ω resistor connects points a and b, at the end of the rails. A bar is in contact with the rails, and is moved by an external force with a constant horizontal velocity of 0.90 m/s to the right, as shown. The bar and the rails have negligible resistance. At the instant that the bar is 0.20 m from the wire, what are the induced current in the resistor and its direction through the resistor? (μ0 = 4π × 10-7 T ∙ m/A)

Accepted Answer

A)  0.63 μA, from a to b 
B)  0.63 μA, from b to a 
C)  0.32 μA, from a to b 
D)  0.32 μA, from b to a 
E)  1.9 μA, from b to a 
A)  0.63 μA, from a to b 
B)  0.63 μA, from b to a 
C)  0.32 μA, from a to b 
D)  0.32 μA, from b to a 
E)  1.9 μA, from b to a

Question 17

An ideal polarizer with its transmission axis rotated 30° to the vertical is placed in a beam of unpolarized light of intensity 10 W/m2. After passing through the polarizer, what is intensity of the beam?

Accepted Answer

A)  2.5 W/m2 
B)  5.0 W/m2 
C)  8.7 W/m2 
D)  7.5 W/m2 
E)  10 W/m2 
A)  2.5 W/m2 
B)  5.0 W/m2 
C)  8.7 W/m2 
D)  7.5 W/m2 
E)  10 W/m2

Question 18

Each photon in a beam of light has an energy of 4.20 eV. What is the wavelength of this light? (c = 3.00 × 108 m/s, h = 6.626 × 10-34 J ∙ s, 1 eV = 1.60 × 10-19 J)

Accepted Answer

A)  321 nm 
B)  103 nm 
C)  296 nm 
D)  412 nm 
E)  420 nm 
A)  321 nm 
B)  103 nm 
C)  296 nm 
D)  412 nm 
E)  420 nm

Question 19

A blacksmith is flattening a steel plate having dimensions 10 cm × 15 cm × 1 mm. He has heated the plate to 900 K. If the emissivity of the plate is 0.75, at what rate does it lose energy by radiation? Ignore any heat exchange with the surroundings. 
(σ = 5.67 × 10-8 W/m2 ∙ K4)

Accepted Answer

A)  360 W 
B)  760 W 
C)  790 W 
D)  850 W 
E)  880 W 
A)  360 W 
B)  760 W 
C)  790 W 
D)  850 W 
E)  880 W

Question 20

If the surface of our bodies is at 37°C, at what wavelength does the radiation that we emit peak if we behave like a blackbody? The constant in Wien's law is 0.0029 m ∙ K.

Accepted Answer

The answer of If the surface of our bodies is...

Exam 25: EM Induction and Em Waves

By what primary heat transfer mechanism does the sun warm the earth?

How far does a beam of light travel in 2.0 ms? (c = 3.0 × 108 m/s)

What is the wavelength used by a radio station that broadcasts at a frequency of 920 kHz? (c = 3.00 × 108 m/s)

A giant star radiates energy at the rate of 3.0 × 1030 W, and its surface temperature has been measured to be 3000 K. Assuming that it is a perfect emitter, what is the radius of this star?(σ = 5.67 × 10-8 W/m2 ∙ K4)

What is the surface temperature of a star, if its radiation peak occurs at a frequency of 1.06 × 1015 Hz? (c = 3.00 × 108 m/s, and the constant in Wien's law is 0.00290 m ∙ K)

As shown in the figure, a metal bar is in contact with a pair of parallel rails and is in motion with an upward velocity of magnitude ν. A uniform magnetic field is present, directed downward as shown. The direction of the induced current through the resistor R is

About 1350 W/m2 of electromagnetic energy reaches the upper atmosphere of the earth from the sun, which is 1.5 × 1011 m away. Use this information to estimate the average power output of the sun.

A bar magnet is oriented above a copper ring, as shown in the figure. If the magnet is kept fixed while the ring is dropped, what is the direction of the current induced in the ring, as viewed from below the ring?

In an electromagnetic wave in free space, the electric and magnetic fields are

An ideal polarizer with its transmission axis rotated 30° to the vertical is placed in a beam of unpolarized light of intensity 10 W/m2. After passing through the polarizer, what is intensity of the beam?

Each photon in a beam of light has an energy of 4.20 eV. What is the wavelength of this light? (c = 3.00 × 108 m/s, h = 6.626 × 10-34 J ∙ s, 1 eV = 1.60 × 10-19 J)

A blacksmith is flattening a steel plate having dimensions 10 cm × 15 cm × 1 mm. He has heated the plate to 900 K. If the emissivity of the plate is 0.75, at what rate does it lose energy by radiation? Ignore any heat exchange with the surroundings. (σ = 5.67 × 10-8 W/m2 ∙ K4)

If the surface of our bodies is at 37°C, at what wavelength does the radiation that we emit peak if we behave like a blackbody? The constant in Wien's law is 0.0029 m ∙ K.

Representing Motion

Motion in One Dimension

Vectors and Motion in Two Dimensions

Forces and Newtons Laws of Motion

Applying Newtons Laws

Gravity

Rotational Motion

Equilibrium Ad Elasticity

Momentum

Energy and Work

Using Energy

Thermal Properties of Matter

Fluids

Oscillations

Traveling Waves and Sound

Superposition and Standing Waves

Wave Optics

Ray Optics

Optical Instruments

Electric Fields and Forces

Electric Potential

Current and Resistance

Circuits

Magnetic Fields and Forces

AC Electricity

Relativity

Quantum Physics

Atoms and Molecules

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Filters

How far does a beam of light travel in 2.0 ms? (c = 3.0 × 10⁸ m/s)

What is the wavelength used by a radio station that broadcasts at a frequency of 920 kHz? (c = 3.00 × 10⁸ m/s)

A giant star radiates energy at the rate of 3.0 × 10³⁰ W, and its surface temperature has been measured to be 3000 K. Assuming that it is a perfect emitter, what is the radius of this star?(σ = 5.67 × 10^-8 W/m² ∙ K⁴)

What is the surface temperature of a star, if its radiation peak occurs at a frequency of 1.06 × 10¹⁵ Hz? (c = 3.00 × 10⁸ m/s, and the constant in Wien's law is 0.00290 m ∙ K)

About 1350 W/m² of electromagnetic energy reaches the upper atmosphere of the earth from the sun, which is 1.5 × 10¹¹ m away. Use this information to estimate the average power output of the sun.

An ideal polarizer with its transmission axis rotated 30° to the vertical is placed in a beam of unpolarized light of intensity 10 W/m². After passing through the polarizer, what is intensity of the beam?

Each photon in a beam of light has an energy of 4.20 eV. What is the wavelength of this light? (c = 3.00 × 10⁸ m/s, h = 6.626 × 10^-34 J ∙ s, 1 eV = 1.60 × 10^-19 J)

A blacksmith is flattening a steel plate having dimensions 10 cm × 15 cm × 1 mm. He has heated the plate to 900 K. If the emissivity of the plate is 0.75, at what rate does it lose energy by radiation? Ignore any heat exchange with the surroundings. (σ = 5.67 × 10^-8 W/m² ∙ K⁴)