Chapter 28

Question 1

An electron moves in the plane of this screen toward thetop of the screen. A magnetic field is also in the plane ofthe screen and directed toward the right. What is thedirection of the magnetic force on the electron?

Answer 1

out of the screen

Question 2

A charged particle is moving perpendicular to a magneticfield in a circle with a radius r.An identical particle enters the field, withperpendicular to , but with a higher speed than thefirst particle. Compared with the radius of the circlefor the first particle, is the radius of thvBe circular pathfor the second particle
(a) smaller,
(b) larger, or
(c) equal in size?

Answer 2

b

Question 3

A charged particle is moving perpendicular to a magneticfield in a circle with a radius r.The magnitude of the magnetic field is increased.Compare the radius of the new circular path of the firstparticle with the radius of its initial path.
(a) smaller,
(b) larger, or
(c) equal in size

Answer 3

a

Question 4

A wire carries current in the plane of this screen towardthe top of the screen. The wire experiences a magneticforce toward the right edge of the screen. Is the directionof the magnetic field causing this force

Answer 4

Out of the screen

Question 5

A spatially uniform magnetic field cannot exert amagnetic force on a particle in which of the following circumstances? There may be more than one correctstatement.

1. The particle is charged.
2. The particle moves perpendicular to the magneticfield.
3. The particle moves parallel to the magnetic field.
4. The magnitude of the magnetic field changes withtime.
5. The particle is at rest

Answer 5

3, 5

Question 6

Rank the magnitudes of the forces exerted on the following particlesfrom largest to smallest. In your ranking, display any cases of equality.
a) an electron moving at 1 Mm/s perpendicular to a 1-mT magneticfield
(b) an electron moving at 1 Mm/s parallel to a 1-mT magnetic field
(c) an electron moving at 2 Mm/s perpendicular to a 1-mT magneticfield(
d) a proton moving at 1 Mm/s perpendicular to a 1-mT magnetic field
(e) a proton moving at 1 Mm/s at a 458 angle to a 1-mT magnetic field

1. d > a = c > b > f
2. a > c > d > b = c
3. c > a = d > e > b
4. b > f > c > d > a
5. b > c > a > f > d

Answer 6

3

Question 7

At a certain instant, a proton is moving in the positivex direction through a magnetic field in the negative zdirection. What is the direction of the magnetic forceexerted on the proton?
1. positive z direction
2. negative z direction
3. positive y direction
4. negative y direction
5. The force is zero

Answer 7

3

Question 8

A thin copper rod 1.00 m long has a mass of 50.0 g.What is the minimum current in the rod that wouldallow it to levitate above the ground in a magneticfield of magnitude 0.100 T?
1. 1.20 A
2. 2.40 A
3. 4.90 A
4. 9.80 A
5. none of those answers

Answer 8

3

Question 9

Electron A is fired horizontally with speed 1.00 Mm/sinto a region where a vertical magnetic field exists.Electron B is fired along the same path with speed2.00 Mm/s. Which electron has a larger magnetic forceexerted on it?1. A does.
2. B does.
3. The forces have the same nonzero magnitude.
4. The forces are both zero

Answer 9

2

Question 10

Electron A is fired horizontally with speed 1.00 Mm/sinto a region where a vertical magnetic field exists.Electron B is fired along the same path with speed2.00 Mm/s. Which electron has a path that curvesmore sharply?
1. A does.
2. B does.
3. The particles follow the same curved path.
4. The particles continue to go straight.

Answer 10

1

Question 11

A magnetic field exerts a torque on each of the currentcarrying single loops of wire shown in the figure. Theloops lie in the xy plane, each carrying the samemagnitude current, and the uniform magnetic fieldpoints in the positive x direction. Rank the loops bythe magnitude of of the torque exerted on them by thefield from largest to smallest
1. AA > AC > AB
2. AB > AA > AC
3. Ac > AB > AA
4. AA > AB > AC

Answer 11

1