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{{Chapter 28Chapter 28

Sources of Magnetic Field (cont.)Sources of Magnetic Field (cont.)

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The long, straight wire AB carries a 14.0-A current as shown. The rectangular loop has long edges parallel to AB and carries a clockwise 5.00-A current.

What is the direction of the net magnetic force that the straight wire AB exerts on the loop?

Q28.5

A. to the right

B. to the left

C. upward (toward AB)

D. downward (away from AB)

E. The net magnetic force is zero

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A28.5

The long, straight wire AB carries a 14.0-A current as shown. The rectangular loop has long edges parallel to AB and carries a clockwise 5.00-A current.

What is the direction of the net magnetic force that the straight wire AB exerts on the loop?

A. to the right

B. to the left

C. upward (toward AB)

D. downward (away from AB)

E. The net magnetic force is zero

© 2012 Pearson Education, Inc.

Q28.6

A wire consists of two straight sections with a semicircular section between them. If current flows in the wire as shown, what is the direction of the magnetic field at P due to the current?

A. to the right

B. to the left

C. out of the plane of the figure

D. into the plane of the figure

E. misleading question—the magnetic field at P is zero

© 2012 Pearson Education, Inc.

A wire consists of two straight sections with a semicircular section between them. If current flows in the wire as shown, what is the direction of the magnetic field at P due to the current?

A28.6

A. to the right

B. to the left

C. out of the plane of the figure

D. into the plane of the figure

E. misleading question—the magnetic field at P is zero

© 2012 Pearson Education, Inc.

The wire shown here is infinitely long and has a 90° bend. If current flows in the wire as shown, what is the direction of the magnetic field at P due to the current?

Q28.7

A. to the right

B. to the left

C. out of the plane of the figure

D. into the plane of the figure

E. none of these

© 2012 Pearson Education, Inc.

The wire shown here is infinitely long and has a 90° bend. If current flows in the wire as shown, what is the direction of the magnetic field at P due to the current?

A28.7

A. to the right

B. to the left

C. out of the plane of the figure

D. into the plane of the figure

E. none of these

© 2012 Pearson Education, Inc.

Q28.8

The figure shows, in cross section, three conductors that carry currents perpendicular to the plane of the figure.

If the currents I1, I2, and I3 all have the same magnitude, for which path(s) is the line integral of the magnetic field equal to zero?

A. path a only

B. paths a and c

C. paths b and d

D. paths a, b, c, and d

E. The answer depends on whether the integral goes clockwise or counterclockwise around the path.

© 2012 Pearson Education, Inc.

The figure shows, in cross section, three conductors that carry currents perpendicular to the plane of the figure.

If the currents I1, I2, and I3 all have the same magnitude, for which path(s) is the line integral of the magnetic field equal to zero?

A28.8

A. path a only

B. paths a and c

C. paths b and d

D. paths a, b, c, and d

E. The answer depends on whether the integral goes clockwise or counterclockwise around the path.

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Paramagnetism, Diamagnetism, Paramagnetism, Diamagnetism, FerromagnetismFerromagnetism

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Hysteresis in Ferromagnetic MaterialsHysteresis in Ferromagnetic Materials

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{{Chapter 29Chapter 29

Electromagnetic InductionElectromagnetic Induction

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Induced currentInduced current A changing magnetic flux causes an A changing magnetic flux causes an induced induced

currentcurrent. See Figure 29.1 below.. See Figure 29.1 below. The The induced emfinduced emf is the corresponding emf causing is the corresponding emf causing

the current.the current.

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Magnetic flux through an area elementMagnetic flux through an area element Figure 29.3 below shows how to calculate the Figure 29.3 below shows how to calculate the

magnetic flux through an element of area.magnetic flux through an element of area.

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Direction of the induced emfDirection of the induced emf

• Follow the text discussion on the direction of the Follow the text discussion on the direction of the induced emf, using Figure 29.6 below.induced emf, using Figure 29.6 below.

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A circular loop of wire is in a region of spatially uniform magnetic field. The magnetic field is directed into the plane of the figure. If the magnetic field magnitude is constant,

Q29.1

A. the induced emf is clockwise.

B. the induced emf is counterclockwise.

C. the induced emf is zero.

D. The answer depends on the strength of the field.

© 2012 Pearson Education, Inc.

A circular loop of wire is in a region of spatially uniform magnetic field. The magnetic field is directed into the plane of the figure. If the magnetic field magnitude is constant,

A29.1

A. the induced emf is clockwise.

B. the induced emf is counterclockwise.

C. the induced emf is zero.

D. The answer depends on the strength of the field.