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Test 6Due: 11:59pm on Sunday, April 24, 2011

Note: You will receive no credit for late submissions. To learn more, read your instructor's Grading Policy

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Exercise 31.7In each circuit described next, an ac voltage source producing a current is connected to an

additional circuit element.

Part A

The ac source is connected across a resistor . Sketch graphs of the current in the circuit and the

potential difference across the resistor as functions of time, covering one cycle of oscillation. Put bothgraphs on the same set of axes so you can compare them.

ANSWER:

View Answer Requested

Part B

Do the same as in part A, except suppose the resistor is replaced by an inductor . Sketch the same

graphs as in part A, but this time across the inductor instead of the resistor.

ANSWER:


Part C

Do the same as in part A, except suppose the resistor is replaced by an capacitor . Sketch the same

graphs as in part A, but this time across the capacitor instead of the resistor.

MasteringPhysics: Assignment Print View http://session.masteringphysics.com/myct/assignmentPrintView?assignme...

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ANSWER:


Part D

Sketch phasor diagram for resistor.

Draw the phasors with their tails at the dot. The orientation of your vectors will be graded. Theexact length of your vectors will not be graded.

ANSWER:

View Correct

Part E

Sketch phasor diagram for inductor.


ANSWER:

View Correct

Part F

Sketch phasor diagram for capacitor.



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ANSWER:

View Correct

Exercise 31.26In a series L-R-C circuit, the components have the following values: 20.0 , 140 , and

350 . The generator has an rms voltage of 120 and a frequency of 1.25 .

Part A

Determine the average power supplied by the generator.

ANSWER: = 7.32Correct

Part B

Determine the average power dissipated in the resistor.


Problem 31.51An - - series circuit is connected to an ac source of constant voltage amplitude and variable angular

frequency .

Part A

Find the current amplitude, as a function of .

Express your answer in terms of the variables , , , , and .

ANSWER:

=


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Correct

Part B

Find the average power dissipated in the resistor.

Express your answer in terms of the variables , , , , and .

ANSWER:

=

Correct

Part C

Show that and are both maximum when ; that is, when the source frequency equals the

resonance frequency of the circuit.

Essay answers are limited to about 500 words (3800 characters maximum, including spaces).

ANSWER: My Answer:

Part D

Graph as a function of for = 100 , = 200 , = 2.0 , and = 0.50 .

ANSWER:

View Correct

Part E

Compare to the light purple curve in the Figure 31.19 in the textbook. Discuss the behavior of and in

the limits = 0 and .


ANSWER: My Answer:


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Problem 31.55: Parallel Resonance

The impedance of an - - parallel circuit is .

Part A

Show that at the resonance angular frequency , and is a minimum.


ANSWER: My Answer:

Part B

Since is a minimum at resonance, is it correct to say that the power delivered to the resistor is also a

minimum at ?

ANSWER: it is correct

it is not correct

Correct

Part C

Explain.


ANSWER: My Answer:

Part D

At resonance, what is the phase angle of the source current with respect to the source voltage?

ANSWER: source current leads the source voltage by = 0Correct

Part E

How does this compare to the phase angle for an series circuit at resonance?

ANSWER: Phase angles are different.

Phase angles are the same.


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Correct

Part F

Draw the circuit diagram for an - - parallel circuit.

Draw the phasors with their tails at the dot. The orientation of your vectors will be graded. Theexact length of your vectors will not be graded but the relative length of one to the other will begraded.

ANSWER:

View All attempts used; correct answer displayed

Part G

Justify the following statement: When the angular frequency of the source is there is no currentflowing between the part of the circuit that includes the source and the resistor.

ANSWER: Yes, statement is valid.

No, statement is invalid.

Correct

Part H

Justify the following statement: When the angular frequency of the source is there is no currentflowing between the part that includes the inductor and capacitor, so you could cut the wires connectingthese two parts of the circuit without affecting the currents.

ANSWER: Yes, statement is valid.

No, statement is invalid.

Correct

Part I


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Is the statement in part H still valid if we consider that any real inductor or capacitor also has someresistance of its own?

ANSWER: Yes, it is.

No, it is not.

Correct

Part J

Explain your answer in part I.


ANSWER: My Answer:

Problem 31.58An - - series circuit consists of a 2.20 capacitor, a 5.50 inductor, and a 50.0 resistor

connected across an ac source of voltage amplitude 18.0 having variable frequency.

Part A

At what frequency is the average power delivered to the circuit equal to ?

ANSWER: = 1.99×104

Correct

Part B

Under the conditions of part (a), what is the average power delivered to each circuit element?

Enter your answers numerically separated by commas.

ANSWER: = 0.810,0,0Correct

Part C

What is the maximum current through the capacitor?



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Problem 32.38

Part A

For a sinusoidal electromagnetic wave in vacuum, such as that described by the equations and , find the average energy density in the

electric field in terms of the average energy density in the magnetic field ( ).

Express your answer in terms of the variable and appropriate constants.

ANSWER: = All attempts used; correct answer displayed

Exercise 32.25An intense light source radiates uniformly in all directions. At a distance of 5.6 from the source theradiation pressure on a perfectly absorbing surface is 6.6×10−6 .

Part A

What is the total average power output of the source?

Express your answer using two significant figures.

ANSWER: = 7.8×105

Correct

Problem 32.45Two square reflectors, each 2.00 on a side and of mass 4.00 , are located at opposite ends of a thin,extremely light, 1.00- rod that can rotate without friction and in a vacuum about an axle perpendicular to itthrough its center (the figure ). These reflectors aresmall enough to be treated as point masses inmoment-of-inertia calculations. Both reflectors areilluminated on one face by a sinusoidal light wavehaving an electric field of amplitude 1.15 that falls

uniformly on both surfaces and always strikes themperpendicular to the plane of their surfaces. Onereflector is covered with a perfectly absorbing coating,and the other is covered with a perfectly reflectingcoating.

Part A


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What is the angular acceleration of this device?

ANSWER: = 5.85×10−13

Correct

Problem 32.49

Part A

A circular loop of wire can be used as a radio antenna. If a 21.0-cm-diameter antenna is located 2.40

away from a 94.0-MHz source with a total power of 65.0 , what is the maximum emf induced in the

loop? (Assume that the plane of the antenna loop is perpendicular to the direction of the radiation'smagnetic field and that the source radiates uniformly in all directions.)

ANSWER: = 5.61×10−2

Correct

Problem 32.57Electromagnetic radiation is emitted by accelerating charges. The rate at which energy is emitted from an

accelerating charge that has charge and acceleration is given by where is the speed of

light.

Part A

If a proton with a kinetic energy of 5.7 is traveling in a particle accelerator in a circular orbit with a

radius of 0.800 , what fraction of its energy does it radiate per second?


ANSWER: = 1.2×10−11

Correct

Part B

Consider an electron orbiting with the same speed and radius. What fraction of its energy does it radiateper second?


ANSWER: = 2.1×10−8

Correct


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Exercise 33.6Light of a certain frequency has a wavelength of 438 in water.

Part A

What is the wavelength of this light in benzene having a refractive index of 1.501?

ANSWER: = 3.89×10−7

Correct

Exercise 33.29A beam of polarized light passes through a polarizing filter. When the angle between the polarizing axis of thefilter and the direction of polarization of the light is , the intensity of the emerging beam is .

Part A

If you now want the intensity to be , what should be the angle (in terms of ) between the polarizing

angle of the filter and the original direction of polarization of the light?

Express your answer in terms of the given variable.

ANSWER:

=

Correct

Exercise 33.7A parallel beam of light in air makes an angle of 53.0 with the surface of a glass plate having a refractive

index of 1.69.

Part A

What is the angle between the reflected part of the beam and the surface of the glass?


Part B

What is the angle between the refracted beam and the surface of the glass?


Exercise 33.31Unpolarized light of intensity 20.6 is incident on two polarizing filters. The axis of the first filter is at an

angle of 23.6 counterclockwise from the vertical (viewed in the direction the light is traveling) and the axis of

the second filter is at 60.2 counterclockwise from the vertical.

Part A

What is the intensity of the light after it has passed through the second polarizer?


Problem 33.40


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In a physics lab, light with a wavelength of 490 travels in air from a laser to a photocell in a time of 17.6 . When a slab of glass with a thickness of 0.820 is placed in the light beam, with the beam incident

along the normal to the parallel faces of the slab, it takes the light a time of 21.1 to travel from the laser tothe photocell.

Part A

What is the wavelength of the light in the glass?

Use 3.00×108 for the speed of light in a vacuum. Express your answer using two significant

figures.

ANSWER: = 210Correct

Problem 33.44A glass plate 3.45 thick, with an index of refraction of 1.35, is placed between a point source of light withwavelength 520 (in vacuum) and a screen. The distance from source to screen is 1.95 .

Part A

How many wavelengths are there between the source and the screen?

ANSWER: 3.98×104

Correct

Exercise 33.12A horizontal, parallel-sided plate of glass having a refractive index of 1.52 is in contact with the surface ofwater in a tank. A ray coming from above in air makes an angle of incidence of 33.0 with the normal to the

top surface of the glass.

Part A

What angle does the ray refracted into the water make with the normal to the surface?

Use 1.33 for the index of refraction of water.

ANSWER: = 0.422Correct radians

Part B

What is the dependence of this angle on the refractive index of the glass?



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ANSWER: My Answer:

Score Summary:Your score on this assignment is 85.8%.You received 85.75 out of a possible total of 100 points.


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