Exercise 28.10
A short current element = (0.500 ) carries a current of 4.60 in the same direction as . Point is located at = ( -0.730 ) + (0.390 ) .
Part A
Find the magnetic field at produced by this current element.
Enter the , , and components of the magnetic field separated by commas.
ANSWER:
Exercise 28.24
A rectangular loop with dimensions 4.20 by 9.50 carries current . The current in the loop produces a magnetic field at the center of the loop that has magnitude 5.20×10−5 and direction away from you as you view the plane of the loop.
Part A
What is the magnitude of the current in the loop?
Express your answer with the appropriate units.
ANSWER:
Part B
What is the direction of the current in the loop?
ANSWER:
Exercise 28.36
A closely wound, circular coil with radius 2.20 has 760 turns.
dl ⃗ mm ĵ A dl ⃗ P
r ⃗ m î m k̂
P
x y z
, , = dBx dBy dBz T
cm cm I T
= I
clockwise
counterclockwise
cm
Part A
What must the current in the coil be if the magnetic field at the center of the coil is 0.0760 ?
Express your answer to three significant figures and include the appropriate units.
ANSWER:
Part B
At what distance from the center of the coil, on the axis of the coil, is the magnetic field half its value at the center?
Express your answer to three significant figures and include the appropriate units.
ANSWER:
Exercise 28.39
Two round concentric metal wires lie on a tabletop, one inside the other. The inner wire has a diameter of 23.0 and carries a clockwise current of 16.0 , as viewed from above, and the outer wire has a diameter of 40.0 .
Part A
What must be the direction (as viewed from above) of the current in the outer wire so that the net magnetic field due to this combination of wires is zero at the common center of the wires?
ANSWER:
Part B
What must be the magnitude of the current in the outer wire so that the net magnetic field due to this combination of wires is zero at the common center of the wires?
ANSWER:
Exercise 28.34
Part A
T
= I
x
= x
cm A cm
The current’s direction must be clockwise.
The current’s direction must be counterclockwise.
= I A
Calculate the magnitude of the magnetic field at point P due to the current in the semicircular section of wire shown in the figure . (Hint: Does the current in the long, straight section of the wire produce any field at P?)
Express your answer in terms of the variables , and appropriate constants.
ANSWER:
Part B
Find the direction of the magnetic field at point P.
ANSWER:
Exercise 28.26
Four very long, current-carrying wires in the same plane intersect to form a square with sidelengths 32.0 , as shown in the figure .
I R
into the page
out of the page
cm
Part A
Find the magnitude of the current so that the magnetic field at the center of the square is zero.
Express your answer using two significant figures.
ANSWER:
Part B
Find the direction of the current so that the magnetic field at the center of the square is zero.
ANSWER:
Exercise 28.44
A solid conductor with radius a is supported by insulating disks on the axis of a conducting tube with inner radius and outer radius (). The central conductor and tube carry currents and correspondingly in the same direction. The currents are distributed uniformly over the cross sections of each conductor. Derive an expression for the magnitude of the magnetic field
Part A
at points outside the central, solid conductor but inside the tube
Express your answer in terms of the variables , , ( ), and appropriate constants ( and ).
ANSWER:
I
= I A
I
upward
downward
b c I1 I2
I1 I2 r a < r c μ0 π
= B(r)
cm
A
= B T
A cm T
= Km
= χm
Part A
A vertical wire carries a current straight down. To the east of this wire, the magnetic field points
ANSWER:
Conceptual Question 28.04
Part A
Two long parallel wires placed side-by-side on a horizontal table carry identical size currents in opposite directions. The wire on your right carries current toward you, and the wire on your left carries current away from you. From your point of view, the magnetic field at the point exactly midway between the two wires
ANSWER:
Conceptual Question 28.09
Part A
Two very long parallel wires in the xy-plane, a distance 2 apart, are parallel to the y-axis and carry equal currents as shown in the figure. The + direction points perpendicular to the xy-plane in a right-handed coordinate system. If both currents flow in the + direction, which one of the graphs shown in the figure below best represents the component of the net magnetic field, in the xy-plane, as a function of ? (Caution: These graphs are not magnetic field lines.)
toward the south.
toward the north.
toward the west.
downward.
toward the east.
points downward.
points upward.
is zero.
points toward you.
points away from you.
a I z
y z x
ANSWER:
Conceptual Question 28.10
Part A
Two very long parallel wires in the xy-plane, a distance 2 apart, are parallel to the y-axis and carry equal currents as shown in the figure. The + direction points perpendicular to the xy-plane in a right-handed coordinate system. If the left current flows in the + direction and the right current flows in the -y direction, which one of the graphs shown in the figure below best represents the component of the net magnetic field, in the xy-plane, as a function of ? (Caution: These graphs are not magnetic field lines.)
1
2
3
4
5
a I z
y z x
ANSWER:
Conceptual Question 28.11
Part A
1
2
3
4
5
The figure shows three long, parallel current-carrying wires. The magnitudes of the currents are equal and their directions are indicated in the figure. Which of the arrows drawn near the wire carrying current 1 correctly indicates the direction of the magnetic force acting on that wire?
ANSWER:
Conceptual Question 28.13
Part A
A long straight conductor has a constant current flowing to the right. A wire rectangle is situated above the wire, and also has a constant current flowing through it (as shown in the figure). Which of the following statements is true?
ANSWER:
A
B
C
D
The magnetic force on current 1 is equal to zero.
Conceptual Question 28.15
Part A
A very long, hollow, thin-walled conducting cylindrical shell (like a pipe) of radius carries a current along its length uniformly distributed throughout the thin shell. Which one of the graphs shown in the figure most accurately describes the magnitude of the magnetic field produced by this current as a function of the distance from the central axis?
ANSWER:
The net magnetic force on the wire rectangle is zero, and the net torque on it is zero.
The net magnetic force on the wire rectangle is downward, and the net torque on it is zero.
The net magnetic force on the wire rectangle is downward, and there is also a net torque on the it.
The net magnetic force on the wire rectangle is zero, but there is a net torque on it.
The net magnetic force on the wire rectangle is upward, and there is also a net torque on the it.
R
B r
Conceptual Question 28.17
Part A
Consider a solenoid of length , windings, and radius ( is much longer than ). A current is flowing through the wire. If the radius of the solenoid were doubled (becoming 2b), and all other quantities remained the same, the magnetic field inside the solenoid would
ANSWER:
Prelecture Concept Question 28.04
Part A
Two long parallel wires are placed side by side on a horizontal table. The wires carry equal currents in the same direction. Which of the following statements are true?
Check all that apply.
ANSWER:
Prelecture Concept Question 28.01
1
2
3
4
5
L N b L b I
become one half as strong.
become twice as strong.
remain the same.
The magnetic force between the two wires is attractive.
The magnetic field at a point midway between the two wires is zero.
The magnetic field is a maximum at a point midway between the two wires.
The magnetic force between the two wires is repulsive.
Part A
Which of the following statements are true concerning the creation of magnetic fields?
Check all that apply.
ANSWER:
Problem 28.04
Part A
A very long thin wire produces a magnetic field of 5×10−3 × 10-4 T at a distance of 1 mm. from the central axis of the wire. What is the magnitude of the current in the wire? (μ 0 = 4π × 10-7 T · m/A)
ANSWER:
Problem 28.02
Part A
A point charge Q moves on the x-axis in the positive direction with a speed of 370 m/s. A point P is on the y-axis at y = +50 mm. The magnetic field produced at point P, as the charge moves through the origin, is equal to -0.7 μT . When the charge is at x = +40 mm, what is the magnitude of the magnetic field at point P? (μ 0 = 4π × 10-7 T · m/A)
ANSWER:
A distribution of electric charges at rest creates a magnetic field at all points in the surrounding region.
A single stationary electric charge creates a magnetic field at all points in the surrounding region.
An electric current in a conductor creates a magnetic field at all points in the surrounding region.
A moving electric charge creates a magnetic field at all points in the surrounding region.
A permanent magnet creates a magnetic field at all points in the surrounding region.
5.0 mA
1.0×104 mA
2.5 mA
7900 mA
k̂
Problem 28.18
Part A
A long straight wire on the -axis carries a current of 6.0 A in the positive direction. A circular loop in the xy-plane, of radius 10 cm, carries a 1.0-A current, as shown in the figure. Point , at the center of the loop, is 25 cm from the -axis. An electron is projected from with a velocity of 1.0 × 106 m/s in the negative -direction. What is the component of the force on the electron? ( = 1.60 × 10-19 C, μ 0 = 4π × 10-7 T · m/A)
ANSWER:
Problem 28.21
0.33 μT
0.63 μT
0.53 μT
0.43 μT
0.73 μT
z P z
P x y
e
-2.0 × 10-18 N
+1.0 × 10-18 N
-1.0 × 10-18 N
+2.0 × 10-18 N
zero
Part A
As shown in the figure, a wire is bent into the shape of a tightly closed omega ( ), with a circular loop of radius 4.0 cm and two long straight sections. The loop is in the xy-plane, with the center at the origin. The straight sections are parallel to the
-axis. The wire carries a 5.0-A current, as shown. What is the magnitude of the magnetic field at the center of the loop? (μ 0 = 4π × 10-7 T · m/A)
ANSWER:
Problem 28.30
Part A
A cylindrical insulated wire of diameter 4.0 mm is tightly wound 300 times around a cylindrical core to form a solenoid with adjacent coils touching each other. When a 0.30 A current is sent through the wire, what is the magnitude of the magnetic field on the axis of the solenoid near its center? (μ 0 = 4π × 10-7 T · m/A)
ANSWER:
Problem 28.68
Ω
x
80 µT
25 µT
40 µT
54 µT
104 µT
11.2 × 10-5 T
4.7 × 10-5 T
5.2 × 10-5 T
9.4 × 10-5 T
7.8 × 10-5 T
In the wire shown in segment is an arc of a circle with radius 30.0 , and point is at the center of curvature of the arc. Segment
is an arc of a circle with radius 20.0 , and point is at its center of curvature. Segments and are straight lines of length 10.0 each.
Part A
Calculate the magnitude of the magnetic field at a point due to a current 11.0 in the wire.
Express your answer with the appropriate units
ANSWER:
Part B
What is the direction of magnetic field?
ANSWER:
Score Summary: Your score on this assignment is 0.0%.
You received 0 out of a possible total of 25 points.
BC cm P
DA cm P CD AB
cm
P A
= B
into the page
out of the page

Exercise 23.10
Four electrons are located at the corners of a square 10.0 on a side, with an alpha particle at its midpoint.
Part A
How much work is done by the Coulomb force when the alpha particle moves to the midpoint of one of the sides of the square?
ANSWER:
Exercise 23.2
A point charge is held stationary at the origin. A second charge is placed at point , and the electric potential energy of the pair of charges is . When the second charge is moved to point , the electric force on the charge does
of work.
Part A
What is the electric potential energy of the pair of charges when the second charge is at point ?
Express your answer using two significant figures.
ANSWER:
Exercise 23.16
Two stationary point charges + 3.00 and + 2.00 are separated by a distance of 50.0 . An electron is released from rest at a point midway between the two charges and moves along the line connecting the two charges.
Part A
What is the speed of the electron when it is 10.0 from the + 3.00- charge?
ANSWER:
Exercise 23.39
nm
= W J
q1 q2 a
+5.4 × J10−8 b −1.9 × J10−8
b
J
nC nC cm
cm nC
= v m/s
The electric field at the surface of a charged, solid, copper sphere with radius 0.250 is 3500 , directed toward the center of the sphere. .
Part A
What is the potential at the center of the sphere, if we take the potential to be zero infinitely far from the sphere?
ANSWER:
Conceptual Question 23.01
Part A
If the electric field is zero everywhere inside a region of space, the potential must also be zero in that region.
ANSWER:
Conceptual Question 23.03
Part A
If the electrical potential in a region is constant, the electric field must be zero everywhere in that region.
ANSWER:
Conceptual Question 23.06
Part A
Suppose a region of space has a uniform electric field, directed towards the right, as shown in the figure. Which statement about the electric potential is true?
m N/C
= V V
True
False
True
False
ANSWER:
Conceptual Question 23.08
Part A
Suppose you have two point charges of opposite sign. As you move them farther and farther apart, the potential energy of this system relative to infinity
ANSWER:
Conceptual Question 23.13
Part A
A nonconducting sphere contains positive charge distributed uniformly throughout its volume. Which statements about the potential due to this sphere are true? All potentials are measured relative to infinity. (There may be more than one correct choice.)
Choose all that apply.
ANSWER:
The potential at points and are equal, and the potential at point is higher than the potential at point .A B C A
The potential at all three locations ( , , ) is the same because the field is uniform.A B C
The potential at point is the highest, the potential at point is the second highest, and the potential at point is the lowest.
A B C
The potential at points and are equal, and the potential at point is lower than the potential at point .A B C A
stays the same.
increases.
decreases.
Prelecture Concept Question 23.01
Part A
A positive charge moves in the direction of an electric field. Which of the following statements are true?
Check all that apply.
ANSWER:
Prelecture Concept Question 23.03
Part A
A positive charge is moved from point A to point B along an equipotential surface. How much work is performed or required in moving the charge?
ANSWER:
The potential at the surface is higher then the potential at the center.
The potential at the center of the sphere is zero.
The potential at the center of the sphere is the same as the potential at the surface.
The potential at the center is the same as the potential at infinity.
The potential is highest at the center of the sphere.
The potential energy associated with the charge decreases.
The electric field does positive work on the charge.
The potential energy associated with the charge increases.
The electric field does negative work on the charge.
The electric field does not do any work on the charge.
The amount of work done on the charge cannot be determined without additional information.
Work is both performed and required in moving the charge from point A to point B.
Work is required in moving the positive charge from point A to point B.
No work is performed or required in moving the positive charge from point A to point B.
Work is performed in moving the positive charge from point A to point B.
Prelecture Concept Question 23.06
Part A
Which of the following statements are true?
Check all that apply.
ANSWER:
Problem 23.06
Part A
A +4.0 μC-point charge and a -4.0-μC point charge are placed as shown in the figure. What is the potential difference, A – B, between points and ? ( = 1/4π = 8.99 × 109 N · m2/C2)
ANSWER:
An equipotential surface is a three-dimensional surface on which the electric potential is the same at every point.
Electric field lines and equipotential surfaces are always mutually perpendicular.
The potential energy of a test charge decreases as it moves along an equipotential surface.
When all charges are at rest, the surface of a conductor is always an equipotential surface.
The potential energy of a test charge increases as it moves along an equipotential surface.
V
V A B k ε0
Problem 23.28
Part A
Two long conducting cylindrical shells are coaxial and have radii of 20 mm and 80 mm. The electric potential of the inner conductor, with respect to the outer conductor, is +600 V. What is the maximum electric field magnitude between the cylinders? ( = 1/4π = 8.99 × 109 N · m2/C2)
ANSWER:
Problem 23.37
Part A
In a certain region, the electric potential due to a charge distribution is given by the equation where x and y are measured in meters and is in volts. At which point is the electric field equal to zero?
ANSWER:
96 kV
48 kV
0.00 V
48 V
96 V
k ε0
10,000 V/m
18,000 V/m
22,000 V/m
26,000 V/m
14,000 V/m
V (x, y) = 2xy − − y,x2
V
Problem 24.66
A parallel-plate capacitor is made from two plates 12.0 on each side and 4.50 apart. Half of the space between these plates contains only air, but the other half is filled with Plexiglas of dielectric constant 3.40. (See the figure below.) An 18.0 battery is connected across the plates.
Part A
What is the capacitance of this combination?
ANSWER:
Part B
How much energy is stored in the capacitor?
ANSWER:
Part C
If we remove the Plexiglas, but change nothing else, how much energy will be stored in the capacitor?
ANSWER:
Problem 24.57
= 0.5 m, = 0.5 mx y
= 1 m, = 1 mx y
= 1 m, = 0.5 mx y
= 0.5 m, = 1 mx y
= 0 m, = 0 mx y
cm mm V
= C F
= U J
= U J
Three capacitors having capacitances of 9.0 , 8.0 , and 4.7 are connected in series across a 30- potential difference.
Part A
What is the charge on the 4.7 capacitor?
Express your answer using two significant figures.
ANSWER:
Part B
What is the total energy stored in all three capacitors?
Express your answer using two significant figures.
ANSWER:
Part C
The capacitors are disconnected from the potential difference without allowing them to discharge. They are then reconnected in parallel with each other, with the positively charged plates connected together. What is the voltage across each capacitor in the parallel combination?
Express your answer using two significant figures.
ANSWER:
Part D
What is the total energy now stored in the capacitors?
Express your answer using two significant figures.
ANSWER:
Problem 24.59
In the figure , each capacitance is 7.2 , and each capacitance is 4.8 .
μF μF μF V
μF
= Q3 C
= U J
= V V
= U J
C1 μF C2 μF
Part A
Compute the equivalent capacitance of the network between points a and b.
Express your answer using two significant figures.
ANSWER:
Part B
Compute the charge on the capacitor nearest to a when = 420 .
Express your answer using two significant figures.
ANSWER:
Part C
Compute the charge on the capacitor nearest to b when = 420 .
ANSWER:
Part D
Compute the charge on the capacitor nearest to a and b when = 420 .
Express your answer using two significant figures.
ANSWER:
= Ceq F
C1 Vab V
= Qa1 C
C1 Vab V
= Qb1 C
C2 Vab V
Part E
With 420 across a and b, compute .
Express your answer using two significant figures.
ANSWER:
Problem 24.51
For the capacitor network shown in the Figure , the potential difference across is 12.0 .
Part A
Find the total energy stored in this network.
ANSWER:
Part B
Find the energy stored in the 4.80- capacitor.
ANSWER:
Problem 24.35
= Q2 C
V Vcd
= Vcd V
ab V
= U μJ
μF
= U4.80 μF μJ
Part A
A parallel-plate capacitor consists of two parallel, square plates that have dimensions 1.0 cm by 1.0 cm. If the plates are separated by 5 mm, and the space between them is filled with teflon, what is the capacitance of this capacitor? (The dielectric constant for teflon is 2.1, and ε0 = 8.85 × 10-12 C2/N · m2.)
ANSWER:
Problem 24.32
Part A
A parallel-plate capacitor has a capacitance of 10 mF and is charged with a 20-V power supply. The power supply is then removed and a dielectric material of dielectric constant 4.0 is used to fill the space between the plates. What is the voltage now across the capacitor?
ANSWER:
Problem 24.29
Part A
Each plate of an air-filled parallel-plate air capacitor has an area of 0.0040 m2, and the separation of the plates is 0.080 mm. An electric field of 5.3 × 106 V/m is present between the plates. What is the energy density between the plates? ( = 8.85 × 10-12 C2/N · m2)
ANSWER:
0.37 pF
0.42 pF
0.18 pF
8.9×10−2 pF
5.0 V
80 V
20 V
2.5 V
10 V
ε0
Problem 24.24
Part A
A 8.00-μF parallel-plate capacitor has charges of 60.0 μC on its plates. How much potential energy is stored in this capacitor?
ANSWER:
Score Summary: Your score on this assignment is 0.0%.
You received 0 out of a possible total of 23 points.
210 J/m3
170 J/m3
84 J/m3
250 J/m3
124 J/m3
205 μJ
225 μJ
215 μJ
195 μJ
235 μJ

RELATED QUESTIONS

 

[heading tag=”h2″ align=”center” color=”#000″ style=”lines” color2=”#000″]GET A PREWRITTEN ANSWER @$19.9[/heading]