1. A positive point charge is moving directly toward point P. The magnetic field that the point charge produces at point P Q28.1 1. points from the charge toward point P 2. points from point P toward the charge 3. is perpendicular to the line from the point charge to point P 4. is zero 5. answer depends on the speed of the point charge

2. A positive point charge is moving directly toward point P. The magnetic field that the point charge produces at point P A28.1 1. points from the charge toward point P 2. points from point P toward the charge 3. is perpendicular to the line from the point charge to point P 4. is zero 5. answer depends on the speed of the point charge

3. Two positive point charges move side by side in the same direction with the same velocity. The magnetic force that the upper point charge exerts on the lower one Q28.2 1. is directed toward the upper point charge (that is, the force is attractive) 2. is directed away from the upper point charge (that is, the force is repulsive) 3. is in the direction of the velocity 4. is opposite to the direction of the velocity 5. none of the above

4. Two positive point charges move side by side in the same direction with the same velocity. The magnetic force that the upper point charge exerts on the lower one A28.2 1. is directed toward the upper point charge (that is, the force is attractive) 2. is directed away from the upper point charge (that is, the force is repulsive) 3. is in the direction of the velocity 4. is opposite to the direction of the velocity 5. none of the above

5. A long straight wire lies along the y– axis and carries current in the positive y–direction. A positive point charge moves along the x–axis in the positive x–direction. The magnetic force that the wire exerts on the point charge Q28.3 1. is in the positive x–direction 2. is in the negative x–direction 3. is in the positive y–direction 4. is in the negative y–direction 5. none of the above

6. A long straight wire lies along the y– axis and carries current in the positive y–direction. A positive point charge moves along the x–axis in the positive x–direction. The magnetic force that the wire exerts on the point charge A28.3 1. is in the positive x–direction 2. is in the negative x–direction 3. is in the positive y–direction 4. is in the negative y–direction 5. none of the above

7. Two long, straight wires are oriented perpendicular to the xy– plane. They carry currents of magnitude I in opposite directions a shown. At point P, the magnetic field due to these currents Q28.4 1. is in the positive x–direction 2. is in the negative x–direction 3. is in the positive y–direction 4. is in the negative y–direction 5. none of the above

8. Two long, straight wires are oriented perpendicular to the xy– plane. They carry currents of magnitude I in opposite directions a shown. At point P, the magnetic field due to these currents A28.4 1. is in the positive x–direction 2. is in the negative x–direction 3. is in the positive y–direction 4. is in the negative y–direction 5. none of the above

9. 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? Q28.5 1. to the right 2. to the left 3. out of the plane of the figure 4. into the plane of the figure 5. none of the above

10. 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? A28.5 1. to the right 2. to the left 3. out of the plane of the figure 4. into the plane of the figure 5. none of the above

11. The figure shows, in cross section, three conductors that carry currents perpendicular to the plane of the figure. If the currents I 1, I 2, and I 3 all have the same magnitude, for which path(s) is the line integral of the magnetic field equal to zero? Q28.6 1. path a only 2. paths a and c 3. paths b and d 4. paths a, b, c, and d 5. answer depends on whether the integral goes clockwise or counterclockwise around the path

12. The figure shows, in cross section, three conductors that carry currents perpendicular to the plane of the figure. If the currents I 1, I 2, and I 3 all have the same magnitude, for which path(s) is the line integral of the magnetic field equal to zero? A28.6 1. path a only 2. paths a and c 3. paths b and d 4. paths a, b, c, and d 5. answer depends on whether the integral goes clockwise or counterclockwise around the path