Question 1

A constant current is sent through a helical coil made of flexible wire.The coil:

Accepted Answer

A)  tends to get shorter
B)  tends to get longer
C)  tends to rotate about its axis
D)  produces zero magnetic field at its center
E)  none of the aboveF) A) and E)
G) B) and D)

Question 2

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) A) and D)
G) A) and E)

Question 3

In Ampere's law,  the symbol  is:

Accepted Answer

A)  an infinitesimal piece of the wire that carries current i
B)  in the direction of 
C)  perpendicular to 
D)  a vector whose magnitude is the length of the wire that carries current i
E)  none of the aboveF) A) and B)
G) None of the above

Question 4

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

Accepted Answer

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

Question 5

Two long ideal solenoids (with radii 20 mm and 30 mm respectively) have the same number of turns of wire per unit length.The smaller solenoid is mounted inside the larger, along a common axis.It is observed that there is zero magnetic field within the inner solenoid.The current in the inner solenoid must be:

Accepted Answer

A)  two-thirds the current in the outer solenoid
B)  one-third the current in the outer solenoid
C)  twice the current in the outer solenoid
D)  half the current in the outer solenoid
E)  the same as the current in the outer solenoidF) C) and D)
G) A) and B)

Question 6

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) B) and E)
G) A) and E)

Question 7

In an overhead straight wire, the current is north.The magnetic field due to this current, at our point of observation, is:

Accepted Answer

A)  east
B)  up
C)  north
D)  down
E)  westF) A) and E)
G) A) and D)

Question 8

In the figure, the current element  , the point P, and the three vectors (1, 2, 3) are all in the plane of the page.The direction of  , due to this current element, at the point P is:

Accepted Answer

A)  in the direction marked "1"
B)  in the direction marked "2"
C)  in the direction marked "3"
D)  out of the page
E)  into the pageF) B) and E)
G) All of the above

Question 9

Which graph correctly gives the magnitude of the magnetic field outside an infinitely long, very thin, straight current-carrying wire as a function of the distance r from the wire?

Accepted Answer

A)  I
B)  II
C)  III
D)  IV
E)  VF) B) and D)
G) A) and C)

Question 10

In Ampere's law,  , the integration must be over any:

Accepted Answer

A)  surface
B)  closed surface
C)  path
D)  closed path
E)  closed path that surrounds all the current producing F) A) and B)
G) A) and C)

Question 11

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) D) and E)
G) A) and B)

Question 12

The magnetic field  inside a long ideal solenoid is independent of:

Accepted Answer

A)  the current
B)  the number of turns of wire
C)  the spacing of the windings
D)  the cross-sectional area
E)  the direction of the currentF) B) and E)
G) B) and D)

Question 13

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) A) and D)
G) All of the above

Question 14

A toroid has a square cross section with the length of an edge equal to the radius of the inner surface.The ratio of the magnitude of the magnetic field at the inner surface to the magnitude of the field at the outer surface is:

Accepted Answer

A)  1/4
B)  1/2
C)  1
D)  2
E)  4F) A) and E)
G) C) and D)

Question 15

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) B) and E)
G) A) and C)

Question 16

Two long straight wires pierce the plane of the paper at vertices of an equilateral triangle as shown below.They each carry 2.0 A, out of the paper.The magnetic field at the third vertex (P) has magnitude: -6 T B) 8.7 * 10-6 T C) 1.0 * 10-5 T D) 1.7 * 10-5 T E) 2.0 * 10-5 T" class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

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

Question 17

A solenoid is 3.0 cm long and has a radius of 0.50 cm.It is wrapped with 500 turns of wire carrying a current of 2.0 A.The magnetic field at the center of the solenoid is:

Accepted Answer

A)  9.9 * 10-8 T
B)  1.3 * 10-3 T
C)  4.2 * 10-2 T
D)  16 T
E)  20 TF) C) and D)
G) C) and E)

Question 18

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)  " (\mu\)  0i/4R" F) A) and D)
G) B) and E)

Question 19

Two parallel long wires carry the same current and repel each other with a force F per unit length.If both these currents are doubled and the wire separation tripled, the force per unit length becomes:

Accepted Answer

A)  2F/9
B)  4F/9
C)  2F/3
D)  4F/3
E)  6FF) D) and E)
G) A) and B)

Question 20

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

Exam 29: Magnetic Fields Due to Currents

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 of the path integral around the window frame is:

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

Correct Answer
verified

A solenoid is 3.0 cm long and has a radius of 0.50 cm.It is wrapped with 500 turns of wire carrying a current of 2.0 A.The magnetic field at the center of the solenoid is:

Correct Answer
verified

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

Correct Answer
verified

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

Correct Answer
verified

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
verified

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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The magnetic field inside a long ideal solenoid is independent of:

Correct Answer
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In Ampere's law, the symbol is:

Correct Answer
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In the figure, the current element , the point P, and the three vectors (1, 2, 3) are all in the plane of the page.The direction of , due to this current element, at the point P is:

Correct Answer
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Magnetic field lines inside the solenoid shown are:

Correct Answer
verified

A toroid has a square cross section with the length of an edge equal to the radius of the inner surface.The ratio of the magnitude of the magnetic field at the inner surface to the magnitude of the field at the outer surface is:

Correct Answer
verified

Two long straight wires pierce the plane of the paper at vertices of an equilateral triangle as shown below.They each carry 2.0 A, out of the paper.The magnetic field at the third vertex (P) has magnitude:

Correct Answer
verified

In an overhead straight wire, the current is north.The magnetic field due to this current, at our point of observation, is:

Correct Answer
verified

Which graph correctly gives the magnitude of the magnetic field outside an infinitely long, very thin, straight current-carrying wire as a function of the distance r from the wire?

Correct Answer
verified

A constant current is sent through a helical coil made of flexible wire.The coil:

Correct Answer
verified

In Ampere's law, , the integration must be over any:

Correct Answer
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Correct Answer
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Two parallel long wires carry the same current and repel each other with a force F per unit length.If both these currents are doubled and the wire separation tripled, the force per unit length becomes:

Correct Answer
verified

Exam 29: Magnetic Fields Due to Currents

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 of the path integral around the window frame is:

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

A solenoid is 3.0 cm long and has a radius of 0.50 cm.It is wrapped with 500 turns of wire carrying a current of 2.0 A.The magnetic field at the center of the solenoid is:

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

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

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

The magnetic field inside a long ideal solenoid is independent of:

Correct AnswerverifiedShow Answer

In Ampere's law, the symbol is:

Correct AnswerverifiedShow Answer

In the figure, the current element , the point P, and the three vectors (1, 2, 3) are all in the plane of the page.The direction of , due to this current element, at the point P is:

Correct AnswerverifiedShow Answer

Magnetic field lines inside the solenoid shown are:

Correct AnswerverifiedShow Answer

A toroid has a square cross section with the length of an edge equal to the radius of the inner surface.The ratio of the magnitude of the magnetic field at the inner surface to the magnitude of the field at the outer surface is:

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 2.0 A, out of the paper.The magnetic field at the third vertex (P) has magnitude:

Correct AnswerverifiedShow Answer

In an overhead straight wire, the current is north.The magnetic field due to this current, at our point of observation, is:

Correct AnswerverifiedShow Answer

Which graph correctly gives the magnitude of the magnetic field outside an infinitely long, very thin, straight current-carrying wire as a function of the distance r from the wire?

Correct AnswerverifiedShow Answer

A constant current is sent through a helical coil made of flexible wire.The coil:

Correct AnswerverifiedShow Answer

In Ampere's law, , the integration must be over any:

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

Two parallel long wires carry the same current and repel each other with a force F per unit length.If both these currents are doubled and the wire separation tripled, the force per unit length becomes:

Correct AnswerverifiedShow Answer

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