A positive point charge is moving to the right. The magnetic fieldthat the point charge produces at point P (see diagram below)

Q28.1

A. points in the same direction as .

B. points from point P toward the charge.

C. points out of the page

D. points into the page

E. The answer depends on the speed of the point charge.

+ r v

P

r v

A positive point charge is moving to the right. The magnetic fieldthat the point charge produces at point P (see diagram below)

A28.1

A. points in the same direction as .

B. points from point P toward the charge.

C. points out of the page

D. points into the page

E. The answer depends on the speed of the point charge.

+ r v

P

r v

A positive point charge is moving directly toward point P. Themagnetic field that the point charge produces at point P

Q28.2

A. points from the charge toward point P.

B. points from point P toward the charge.

C. points out of the page

D. points into the page

E. is zero.

+ r v P

A positive point charge is moving directly toward point P. Themagnetic field that the point charge produces at point P

A28.1

A. points from the charge toward point P.

B. points from point P toward the charge.

C. points out of the page

D. points into the page

E. is zero.

+ r v P

Q28.3

A. toward the upper point charge (the force is attractive)

B. away from the upper point charge (the force is repulsive)

C. in the direction of the velocity

D. opposite to the direction of the velocity

E. none of the above

Two positive point charges move side by side in thesame direction with the same velocity.

What is the direction of the magnetic force that theupper point charge exerts on the lower one?

+q rv

+q rv

A28.3

A. toward the upper point charge (the force is attractive)

B. away from the upper point charge (the force is repulsive)

C. in the direction of the velocity

D. opposite to the direction of the velocity

E. none of the above

Two positive point charges move side by side in thesame direction with the same velocity.

What is the direction of the magnetic force that theupper point charge exerts on the lower one?

+q rv

+q rv

A long straight wire lies along the y–axis andcarries current in the positive y–direction.

A positive point charge moves along thex–axis in the positive x–direction. Themagnetic force that the wire exerts on thepoint charge is in

Q28.4

A. the positive x–direction.

B. the negative x–direction.

C. the positive y–direction.

D. the negative y–direction.

E. none of the above

+q

rv

x

y

O

I

A long straight wire lies along the y–axis andcarries current in the positive y–direction.

A positive point charge moves along thex–axis in the positive x–direction. Themagnetic force that the wire exerts on thepoint charge is in

A28.4

A. the positive x–direction.

B. the negative x–direction.

C. the positive y–direction.

D. the negative y–direction.

E. none of the above

+q

rv

x

y

O

I

Q28.5

Two long, straight wires areoriented perpendicular to thexy–plane. They carry currents ofequal magnitude I in oppositedirections as shown. At point P,the magnetic field due to thesecurrents is in

A. the positive x–direction. B. the negative x–direction.

C. the positive y–direction. D. the negative y–direction.

E. none of the above

Two long, straight wires areoriented perpendicular to thexy–plane. They carry currents ofequal magnitude I in oppositedirections as shown. At point P,the magnetic field due to thesecurrents is in

A28.5

A. the positive x–direction. B. the negative x–direction.

C. the positive y–direction. D. the negative y–direction.

E. none of the above

The long, straight wire AB carriesa 14.0-A current as shown. Therectangular loop has long edgesparallel to AB and carries aclockwise 5.00-A current.

What is the direction of the netmagnetic force that the straightwire AB exerts on the loop?

Q28.6

A. to the right B. to the left

C. upward (toward AB) D. downward (away from AB)

E. misleading question — the net magnetic force is zero

The long, straight wire AB carriesa 14.0-A current as shown. Therectangular loop has long edgesparallel to AB and carries aclockwise 5.00-A current.

What is the direction of the netmagnetic force that the straightwire AB exerts on the loop?

A28.6

A. to the right B. to the left

C. upward (toward AB) D. downward (away from AB)

E. misleading question — the net magnetic force is zero

Q28.7

A wire consists of twostraight sections with asemicircular sectionbetween them. If currentflows in the wire as shown,what is the direction of themagnetic field at P due tothe 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

A wire consists of twostraight sections with asemicircular sectionbetween them. If currentflows in the wire as shown,what is the direction of themagnetic field at P due tothe 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. misleading question — the magnetic field at P is zero

The wire shown here isinfinitely long and has a90° bend. If current flowsin the wire as shown, whatis the direction of themagnetic field at P due tothe current?

Q28.8

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

The wire shown here isinfinitely long and has a90° bend. If current flowsin the wire as shown, whatis the direction of themagnetic field at P due tothe current?

A28.8

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

Q28.9

The figure shows, in cross section, threeconductors that carry currentsperpendicular to the plane of the figure.

If the currents I1, I2, and I3 all have thesame magnitude, for which path(s) isthe line integral of the magnetic fieldequal 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 goesclockwise or counterclockwise around the path.

The figure shows, in cross section, threeconductors that carry currentsperpendicular to the plane of the figure.

If the currents I1, I2, and I3 all have thesame magnitude, for which path(s) isthe line integral of the magnetic fieldequal to zero?

A28.9

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 goesclockwise or counterclockwise around the path.

The figure shows, in cross section, twoconductors that carry currentsperpendicular to the plane of the figure.Both current have the same magnitude.

Which of the following statement isNOT true?

Q28.10

A. The line integral of the magnetic field along theAmperian loop is zero

B. The magnetic field is zero along the Amperian loop.

C. The Amperian loop enclosed a net zero current.

D. The dot product B and dl is positive for part of theloop and negative for part of the loop.

dr l

Amperianloop

The figure shows, in cross section, twoconductors that carry currentsperpendicular to the plane of the figure.Both current have the same magnitude.

Which of the following statement isNOT true?

A28.10

A. The line integral of the magnetic field along theAmperian loop is zero

B. The magnetic field is zero along the Amperian loop.

C. The Amperian loop enclosed a net zero current.

D. The dot product B and dl is positive for part of theloop and negative for part of the loop.

dr l

Amperianloop