PHYS 232 Quiz #3

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Multiple choice: 1 pt. each

1. In which of the following scenarios does a particle NOT feel a force in a magnetic field?

A. The particle has a charge and moves parallel to the field.

B. The particle has a charge has zero velocity.

C. The particle is uncharged.

* D. All of the above.

2. On a certain part of the earth, there is a magnetic field that comes out of the ground toward the sky. When a plane flies over this region, positive charges in the planes body move

* A. to the right side of the plane.

B. to the left side of the plane.

C. to the back of the plane.

D. to the front of the plane.

3. As you look at a loop, a current travels around it in a clockwise direction. (This means that the direction of is away from you.) In which direction must a magnetic field point in order for this loop to feel a torque?

A. in the same direction as .

B. in the opposite direction as .

* C. perpendicular to .

D. none of the above. Magnetic fields do not produce torques on current loops.

4. A current travels along the z-axis in the +z direction. At a point along the +x-axis, the magnetic field is pointing in which direction?

A.

* B.

C.

D.

5. Two wires are parallel to each other. When do the wires attract each other?

* A. if both wires have currents in the same direction.

B. if the wires have currents in opposite directions.

C. if one wire carries a current and the other does not.

D. none of the above

6. When the magnetic field is integrated around a particular loop, it is found to be zero. This means that

A. There is no net charge in that loop.

* B. There is no net current going through that loop.

C. Both A and B.

D. Neither A nor B.

7. A disk of radius 0.5 m is made out of metal and is spinning about its axis with a constant angular velocity of 2 rad/s. If there is a constant magnetic field of 5 T throughout the region of the disk, pointing in the same direction as the angular velocity, then

a) What is the force (magnitude and direction) felt by an electron at the edge of the disk? (2 pts)

is pointing radially outward, but the charge is negative, so the force is pointing radially inward.

b) What is the force (magnitude and direction) felt by a proton at a distance of 0.25 m from the center of the disk? (2 pts)

is pointing radially outward, and the charge is positive, so the force is pointing radially outward.