Question 1

The magnetic field outside a long straight current-carrying wire depends on the distance R from the wire axis according to:

Accepted Answer

A)   R
B)   1/R
C)   1/R2
D)   1/R3
E)   1/R3/2F) None of the above
G) A) and D)

Question 2

Magnetic field lines inside the solenoid shown are:

Accepted Answer

A)   clockwise circles as one looks down the axis from the top of the page
B)   counterclockwise circles as one looks down the axis from the top of the page
C)   toward the top of the page
D)   toward the bottom of the page
E)   in no direction since B = 0F) A) and D)
G) B) and D)

Question 3

Two long straight wires pierce the plane of the paper at vertices of an equilateral triangle as shown below. They each carry 2 A, out of the paper. The magnetic field at the third vertex (P)  has magnitude (in T) : -5 B)  1.7* 10-5 C)  2.0 * 10-5 D)  5.0 * 10-6 E)  8.7 *10-6" class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)   1.0 *10-5
B)   1.7* 10-5
C)   2.0 * 10-5
D)   5.0 * 10-6
E)   8.7 *10-6F) C) and D)
G) A) and B)

Question 4

A long straight cylindrical shell carries current i uniformly distributed over its cross section. The magnitude of the magnetic field is greatest:

Accepted Answer

A)   at the inner surface of the shell
B)   at the outer surface of the shell
C)   inside the shell near the middle
D)   in hollow region near the inner surface
E)   near the center of the hollow regionF) A) and B)
G) A) and D)

Question 5

The magnetic field a distance 2 cm from a long straight current-carrying wire is 2 *10-5 T. The current in the wire is:

Accepted Answer

A)   0.16 A
B)   1.0 A
C)   2.0 A
D)   4.0 A
E)   25 AF) D) and E)
G) C) and D)

Question 6

A long straight wire carrying a 3.0 A current enters a room through a window 1.5 m high and 1.0 m wide. The path integral -7 C)  3.0 * 10-7 D)  3.8 *10-6 E)  none of these" class="answers-bank-image d-inline" rel="preload" > around the window frame has the value (in T.m) :

Accepted Answer

A)   0.20
B)   2.5* 10-7
C)   3.0 * 10-7
D)   3.8 *10-6
E)   none of theseF) B) and D)
G) A) and E)

Question 7

Electrons are going around a circle in a counterclockwise direction as shown. At the center of the circle they produce a magnetic field that is:

Accepted Answer

A)   into the page
B)   out of the page
C)   to the left
D)   to the right
E)   zeroF) A) and E)
G) C) and D)

Question 8

The diagram shows three equally spaced wires that are perpendicular to the page. The currents are all equal, two being out of the page and one being into the page. Rank the wires according to the magnitudes of the magnetic forces on them, from least to greatest.

Accepted Answer

A)   1, 2, 3
B)   2, 1 and 3 tie
C)   2 and 3 tie, then 1
D)   1 and 3 tie, then 2
E)   3, 2, 1F) A) and D)
G) A) and B)

Question 9

The magnitude of the magnetic field at point P, at the center of the semicircle shown, is given by: 0i/R2 B)   \mu 0i/2  \pi R C)   \mu 0i/4  \pi R D)   \mu 0i/2R E)   \mu 0i/4R " class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)   2 μ\muμ 0i/R2
B)    μ\muμ 0i/2  π\piπ R
C)    μ\muμ 0i/4  π\piπ R
D)    μ\muμ 0i/2R
E)    μ\muμ 0i/4R F) None of the above
G) All of the above

Question 10

Four long straight wires carry equal currents into the page as shown. The magnetic force exerted on wire F is:

Accepted Answer

A)   north
B)   east
C)   south
D)   west
E)   zeroF) A) and E)
G) A) and D)

Question 11

If R is the distance from a magnetic dipole, then the magnetic field it produces is proportional to:

Accepted Answer

A)   R
B)   1/R
C)   R2
D)   1/R2
E)   1/R3F) B) and D)
G) C) and D) E

Question 12

In Ampere's law,  the direction of the integration around the path:

Accepted Answer

A)   must be clockwise
B)   must be counterclockwise
C)   must be such as to follow the magnetic field lines
D)   must be along the wire in the direction of the current
E)   none of the aboveF) B) and D)
G) B) and C)

Question 13

A hollow cylindrical conductor (inner radius = a, outer radius = b)  carries a current i uniformly spread over its cross section. Which graph below correctly gives B as a function of the distance r from the center of the cylinder?

Accepted Answer

A)   I
B)   II
C)   III
D)   IV
E)   VF) None of the above
G) D) and E)

Question 14

A wire carrying a large current i from east to west is placed over an ordinary magnetic compass. The end of the compass needle marked "N" will point:

Accepted Answer

A)   north
B)   south
C)   east
D)   west
E)   the compass will act as an electric motor, hence the needle will keep rotatingF) None of the above
G) C) and E)

Question 15

Two long straight current-carrying parallel wires cross the x axis and carry currents I and 3I in the same direction, as shown. At what value of x is the net magnetic field zero?

Accepted Answer

A)   0
B)   1
C)   3
D)   5
E)   7F) A) and C)
G) A) and E) C

Question 16

Lines of the magnetic field produced by a long straight wire carrying a current are:

Accepted Answer

A)   in the direction of the current
B)   opposite to the direction of the current
C)   leave the wire radially
D)   are circles concentric with the wire
E)   are lines similar to those produced by a bar magnetF) A) and E)
G) A) and D) E

Question 17

A toroid with a square cross section carries current i. The magnetic field has its largest magnitude:

Accepted Answer

A)   at the center of the hole
B)   just inside the toroid at its inner surface
C)   just inside the toroid at its outer surface
D)   at any point inside (the field is uniform) 
E)   at none of the aboveF) A) and B)
G) B) and D)

Question 18

Two long straight wires enter a room through a window. One carries a current of 3.0 A into the room while the other carries a current of 5.0 A out. The magnitude in T.m of the path integral -6  T .m B)  3.8 * 10-6 T .m C)  6.3 *10-6 T .m D)  1.0 *10-5 T .m E)  none of these" class="answers-bank-image d-inline" rel="preload" > around the window frame is:

Accepted Answer

A)   2.5 *10-6  T .m
B)   3.8 * 10-6 T .m
C)   6.3 *10-6 T .m
D)   1.0 *10-5 T .m
E)   none of theseF) A) and B)
G) C) and D)

Question 19

The diagram shows three arrangements of circular loops, centered on vertical axes and carrying identical currents in the directions indicated. Rank the arrangements according to the magnitudes of the magnetic fields at the midpoints between the loops on the central axes.

Accepted Answer

A)   1, 2, 3
B)   2, 1, 3
C)   2, 3, 1
D)   3, 2, 1
E)   3, 1, 2F) A) and C)
G) B) and C)

Question 20

Two long straight wires are parallel and carry current in the same direction. The currents are 8.0 and 12 A and the wires are separated by 0.40 cm. The magnetic field in tesla at a point midway between the wires is:

Accepted Answer

A)   0
B)   4.0 *10-4
C)   8.0 * 10-4
D)   12 *10-4
E)   20 * 10-4F) B) and C)
G) None of the above

Exam 29: Magnetic Fields Due to Currents

The magnetic field outside a long straight current-carrying wire depends on the distance R from the wire axis according to:

Correct Answer
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Magnetic field lines inside the solenoid shown are:

Correct Answer
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Two long straight wires pierce the plane of the paper at vertices of an equilateral triangle as shown below. They each carry 2 A, out of the paper. The magnetic field at the third vertex (P) has magnitude (in T) :

Correct Answer
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A long straight cylindrical shell carries current i uniformly distributed over its cross section. The magnitude of the magnetic field is greatest:

Correct Answer
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The magnetic field a distance 2 cm from a long straight current-carrying wire is 2 *10^-⁵ T. The current in the wire is:

Correct Answer
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A long straight wire carrying a 3.0 A current enters a room through a window 1.5 m high and 1.0 m wide. The path integral around the window frame has the value (in T.m) :

Correct Answer
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Electrons are going around a circle in a counterclockwise direction as shown. At the center of the circle they produce a magnetic field that is:

Correct Answer
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The diagram shows three equally spaced wires that are perpendicular to the page. The currents are all equal, two being out of the page and one being into the page. Rank the wires according to the magnitudes of the magnetic forces on them, from least to greatest.

Correct Answer
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Correct Answer
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Four long straight wires carry equal currents into the page as shown. The magnetic force exerted on wire F is:

Correct Answer
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If R is the distance from a magnetic dipole, then the magnetic field it produces is proportional to:

Correct Answer
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E

In Ampere's law, the direction of the integration around the path:

Correct Answer
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A hollow cylindrical conductor (inner radius = a, outer radius = b) carries a current i uniformly spread over its cross section. Which graph below correctly gives B as a function of the distance r from the center of the cylinder?

Correct Answer
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A wire carrying a large current i from east to west is placed over an ordinary magnetic compass. The end of the compass needle marked "N" will point:

Correct Answer
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Two long straight current-carrying parallel wires cross the x axis and carry currents I and 3I in the same direction, as shown. At what value of x is the net magnetic field zero?

Correct Answer
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C

Lines of the magnetic field produced by a long straight wire carrying a current are:

Correct Answer
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E

A toroid with a square cross section carries current i. The magnetic field has its largest magnitude:

Correct Answer
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Two long straight wires enter a room through a window. One carries a current of 3.0 A into the room while the other carries a current of 5.0 A out. The magnitude in T.m of the path integral around the window frame is:

Correct Answer
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The diagram shows three arrangements of circular loops, centered on vertical axes and carrying identical currents in the directions indicated. Rank the arrangements according to the magnitudes of the magnetic fields at the midpoints between the loops on the central axes.

Correct Answer
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Two long straight wires are parallel and carry current in the same direction. The currents are 8.0 and 12 A and the wires are separated by 0.40 cm. The magnetic field in tesla at a point midway between the wires is:

Correct Answer
verified

Exam 29: Magnetic Fields Due to Currents

The magnetic field outside a long straight current-carrying wire depends on the distance R from the wire axis according to:

Correct AnswerverifiedShow Answer

Magnetic field lines inside the solenoid shown are:

Correct AnswerverifiedShow Answer

Two long straight wires pierce the plane of the paper at vertices of an equilateral triangle as shown below. They each carry 2 A, out of the paper. The magnetic field at the third vertex (P) has magnitude (in T) :

Correct AnswerverifiedShow Answer

A long straight cylindrical shell carries current i uniformly distributed over its cross section. The magnitude of the magnetic field is greatest:

Correct AnswerverifiedShow Answer

The magnetic field a distance 2 cm from a long straight current-carrying wire is 2 *10-5 T. The current in the wire is:

Correct AnswerverifiedShow Answer

A long straight wire carrying a 3.0 A current enters a room through a window 1.5 m high and 1.0 m wide. The path integral around the window frame has the value (in T.m) :

Correct AnswerverifiedShow Answer

Electrons are going around a circle in a counterclockwise direction as shown. At the center of the circle they produce a magnetic field that is:

Correct AnswerverifiedShow Answer

The diagram shows three equally spaced wires that are perpendicular to the page. The currents are all equal, two being out of the page and one being into the page. Rank the wires according to the magnitudes of the magnetic forces on them, from least to greatest.

Correct AnswerverifiedShow Answer

The magnitude of the magnetic field at point P, at the center of the semicircle shown, is given by:

Correct AnswerverifiedShow Answer

Four long straight wires carry equal currents into the page as shown. The magnetic force exerted on wire F is:

Correct AnswerverifiedShow Answer

If R is the distance from a magnetic dipole, then the magnetic field it produces is proportional to:

Correct AnswerverifiedE

In Ampere's law, the direction of the integration around the path:

Correct AnswerverifiedShow Answer

A hollow cylindrical conductor (inner radius = a, outer radius = b) carries a current i uniformly spread over its cross section. Which graph below correctly gives B as a function of the distance r from the center of the cylinder?

Correct AnswerverifiedShow Answer

A wire carrying a large current i from east to west is placed over an ordinary magnetic compass. The end of the compass needle marked "N" will point:

Correct AnswerverifiedShow Answer

Two long straight current-carrying parallel wires cross the x axis and carry currents I and 3I in the same direction, as shown. At what value of x is the net magnetic field zero?

Correct AnswerverifiedC

Lines of the magnetic field produced by a long straight wire carrying a current are:

Correct AnswerverifiedE

A toroid with a square cross section carries current i. The magnetic field has its largest magnitude:

Correct AnswerverifiedShow Answer

Two long straight wires enter a room through a window. One carries a current of 3.0 A into the room while the other carries a current of 5.0 A out. The magnitude in T.m of the path integral around the window frame is:

Correct AnswerverifiedShow Answer

The diagram shows three arrangements of circular loops, centered on vertical axes and carrying identical currents in the directions indicated. Rank the arrangements according to the magnitudes of the magnetic fields at the midpoints between the loops on the central axes.

Correct AnswerverifiedShow Answer

Two long straight wires are parallel and carry current in the same direction. The currents are 8.0 and 12 A and the wires are separated by 0.40 cm. The magnetic field in tesla at a point midway between the wires is:

Correct AnswerverifiedShow Answer

Correct Answer
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The magnetic field a distance 2 cm from a long straight current-carrying wire is 2 *10^-⁵ T. The current in the wire is:

Correct Answer
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E

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C

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E

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