University Physics Mastering Physics Ch 31 32

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Chapter 31/32 Assignment

Due: 11:00pm on Sunday, April 29, 2012

Note: To understand how points are aw arded, read your instructor's Grading Policy.

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Exercise 31.9

Part A

What is the reactance of an inductor with an inductance of 3.30 at a frequency of 80.0 ?

ANSWER: = 1660

Correct

Part B

What is the inductance of an inductor whose reactance is 12.6 at a frequency of 80.0 ?

ANSWER: = 2.51×10−2

Correct

Part C

What is the reactance of a capacitor with a capacitance of 4.25×10−6 at a frequency of 80.0

?

ANSWER: = 468

Correct

Part D

What is the capacitance of a capacitor whose reactance is 127 at a frequency of 80.0 ?

ANSWER: = 1.57×10−5

Correct

Exercise 31.23

In an L-R-C series circuit, the rms voltage across the resistor is 30.4 , across the capacitor it is

89.0 and across the inductor it is 52.0 .

Part A

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What is the rms voltage of the source?

ANSWER: = 47.9

Correct

Exercise 31.29

An L-R-C series circuit = 0.121 , = 241 , and = 7.25 carries an rms current of

0.449 with a frequency of 405 .

Part A

What is the phase angle?

ANSWER: = 0.811

Correct radians

Part B

What is the power factor for this circuit?

ANSWER: 0.689Correct

Part C

What is the impedance of the circuit?

ANSWER: = 350

Correct

Part D

What is the rms voltage of the source?

ANSWER: = 157

Correct

Part E

What average power is delivered by the source?

ANSWER: = 48.6

Correct



Part FWhat is the average rate at which electrical energy is converted to thermal energy in theresistor?

ANSWER: = 48.6

Correct

Part G

What is the average rate at which electrical energy is dissipated (converted to other forms) inthe capacitor?

ANSWER: 0Correct

Part H

What is the average rate at which electrical energy is dissipated (converted to other forms) inthe inductor?

ANSWER: 0Correct

Exercise 31.35

A series circuit consists of an ac source of variable frequency, a 110 resistor, a 1.20

capacitor, and a 4.90 inductor.

Part A

Find the impedance of this circuit when the angular frequency of the ac source is adjusted tothe resonance angular frequency.

ANSWER: = 110

Correct

Part B

Find the impedance of this circuit when the angular frequency of the ac source is adjusted totwice the resonance angular frequency.

ANSWER: = 146

Correct

Part C

Find the impedance of this circuit when the angular frequency of the ac source is adjusted to



half the resonance angular frequency.

ANSWER: = 146

Correct

Exercise 31.39

You plan to take your hair blower to Europe, where the electrical outlets put out 240 instead of

the 120 seen in the United States. The blower puts out 1700 at 120 .

Part A

What could you do to operate your blower via the 240 line in Europe?

ANSWER:Use a step_up transformer with = 2.

Use a step_down transformer with = 1/2.

Correct

Part B

What current will your blower draw from a European outlet?

Express your answer using two significant figures.

ANSWER: = 7.1

Correct

Part C

What resistance will your blower appear to have when operated at 240 ?


ANSWER: = 34

Correct

Problem 31.47

An - - series circuit consists of a 40.0 resistor, a 18.0 capacitor, a 3.00 inductor,

and an ac voltage source of voltage amplitude 60.0 operating at 1150 .

Part A

Find the current amplitude across the inductor, the resistor, and the capacitor.



ANSWER: = 1.42

Correct

Part B

Find the voltage amplitudes across the inductor, the resistor, and the capacitor.

Enter your answers numerically separated by commas.

ANSWER: = 30.7,56.6,10.9

Correct

Part C

Why can the voltage amplitudes add up to more than 60.0 ?

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

ANSWER: My Answer:Because the source voltage amplitude is the vector sum of V_L, V_R, V_C.

Part D

If the frequency is now doubled, but nothing else is changed, which of the quantities in part Aand B will change?

ANSWER:only voltage amplitude across the inductor and capacitor willchange

only current amplitude will change

only voltage amplitude across the inductor will change

current amplitude and voltage across the any circuit element willchange

Correct

Part E

Find new current amplitude across the inductor, the resistor, and the capacitor.

ANSWER: = 1.07

Correct

Part F

Find new voltage amplitudes across the inductor, the resistor, and the capacitor.



Enter your answers numerically separated by commas.

ANSWER: = 46.3,42.7,4.10

Correct

Exercise 32.8

The electric field of a sinusoidal electromagnetic wave obeys the equation .

Part A

What is the amplitude of the electric field of this wave?

ANSWER: = 375

Correct

Part B

What is the amplitude of the magnetic field of this wave?

ANSWER: = 1.25

Correct

Part C

What is the frequency of the wave?

ANSWER: = 9.50×1014

Correct

Part D

What is the wavelength of the wave?

ANSWER: = 316

Correct

Part E

What is the period of the wave?

ANSWER: = 1.05×10−15

Correct

Part F



Is this light visible to humans?

ANSWER:No, this wavelength is too short to be visible.

Yes, this light is visible to humans.

Correct

Part G

What is the speed of the wave?

ANSWER: = 3.00×108

Correct

Exercise 32.19: Testing a Space Radio Transmitter

You are a NASA mission specialist on your first flight aboard the space shuttle. Thanks to yourextensive training in physics, you have been assigned to evaluate the performance of a new radiotransmitter on board the International Space Station (ISS). Perched on the shuttle's moveable arm,you aim a sensitive detector at the ISS, which is a distance of 2.8 away. You find that the

electric-field amplitude of the radio waves coming from the ISS transmitter is 7.1×10−2 and

that the frequency of the waves is 227 .

Part A

Find the intensity of the radio wave at your location.


ANSWER: = 6.7×10−6

Correct

Part B

Find the magnetic-field amplitude of the wave at your location.


ANSWER: = 2.4×10−10

Correct

Part C

Find the total power output of the ISS radio transmitter.


ANSWER: = 660



Correct

Part D

What assumptions, if any, did you make in your calculations?

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

ANSWER: My Answer:I assumed the International Space Station to be a stationary point in space andthat the radio waves are being distributed evenly.

Exercise 32.22

A sinusoidal electromagnetic wave emitted by a cellular phone has a wavelength of 34.1 and

an electric-field amplitude of 5.30×10−2 at a distance of 300 from the antenna.

Part A

Calculate the frequency of the wave.

ANSWER: = 8.80×108

Correct

Part B

Calculate the magnetic-field amplitude.

ANSWER: = 1.77×10−10

Correct

Part C

Find the intensity of the wave.

ANSWER: = 3.73×10−6

Correct

Exercise 32.35: Microwave Oven

The microwaves in a certain microwave oven have a wavelength of 12.2 .

Part A

How wide must this oven be so that it will contain five antinodal planes of the electric field alongits width in the standing wave pattern?



ANSWER: =

30.5Correct

Part B

What is the frequency of these microwaves?

ANSWER: = 2.46×109

Correct

Part C

Suppose a manufacturing error occurred and the oven was made 4.0 longer than specified

in part (a). In this case, what would have to be the frequency of the microwaves for there still tobe five antinodal planes of the electric field along the width of the oven?

ANSWER: = 2.17×109

Correct

Problem 32.41

A small helium-neon laser emits red visible light with a power of 3.50 in a beam that has a

diameter of 3.10 .

Part A

What is the amplitude of the electric field of the light?

ANSWER: = 591

Correct

Part B

What is the amplitude of the magnetic field of the light?

ANSWER: = 1.97×10−6

Correct

Part C

What is the average energy density associated with the electric field?

ANSWER: = 7.73×10−7

Correct



Part D

What is the average energy density associated with the magnetic field?

ANSWER: = 7.73×10−7

Correct

Part E

What is the total energy contained in a -m length of the beam?

ANSWER: = 1.17×10−11

Correct

Problem 32.45

Two square reflectors, each 2.00 on a side and of mass 5.00 , 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 it through its center (the figure ). These reflectors are small enough to be treatedas point masses in moment-of-inertiacalculations. Both reflectors areilluminated on one face by a sinusoidallight wave having an electric field ofamplitude 1.35 that falls uniformly on

both surfaces and always strikes themperpendicular to the plane of theirsurfaces. One reflector is covered with aperfectly absorbing coating, and the otheris covered with a perfectly reflectingcoating.

Part A

What is the angular acceleration of this device?

ANSWER: = 6.45×10−13

Correct

Problem 32.53: Global Positioning System (GPS)

The GPS network consists of 24 satellites, each of which makes two orbits around the earth perday. Each satellite transmits a 50.0 (or even less) sinusoidal electromagnetic signal at two

frequencies, one of which is 1575.42 . Assume that a satellite transmits half of its power at



each frequency and that the waves travel uniformly in a downward hemisphere.

Part A

What average intensity does a GPS receiver on the ground, directly below the satellite, receive?(Hint: First use Newton's laws to find the altitude of the satellite.)

ANSWER: = 9.75×10−15

Correct

Part B

What is the amplitude of the electric field at the GPS receiver in part (a)?

ANSWER: = 2.71×10−6

Correct

Part C

What is the amplitude of the magnetic field at the GPS receiver in part (a)?

ANSWER: = 9.03×10−15

Correct

Part D

How long does it take the signal to reach the receiver?

ANSWER: = 6.73×10−2

Correct

Part E

If the receiver is a square panel 1.50 on a side that absorbs all of the beam, what average

pressure does the signal exert on it?

ANSWER: = 3.25×10−23

Correct

Part F

What wavelength must the receiver be tuned to?

ANSWER: = 0.190

Correct



Score Summary:

Your score on this assignment is 100%.You received 26 out of a possible total of 26 points.

University Physics Mastering Physics Ch 31 32

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