Download Lesson 2 - cosphysics

Lesson 9.01 Forces on Moving Charges
Lesson 9.02 Forces on Current-carrying Wires in Magnetic Fields
Lesson 9.03 Fields of Long Current-carrying Wires
Self-Check Quiz
1. A particle with positive charge q = 3*10-6 C is at a distance of
1.5*10-2 m from a long vertical wire that carries a current I = 5 A. The
particle is traveling with a speed v = 1000 m/s perpendicular to the
wire and is moving away from the wire. What are the magnitude and
direction of the force on the particle?
a. 1.0*10-8 N up
b. 1.0*10-8 N down
c. 2.0*10-8 N up
d. 2.0*10-8 down
e. 2.0*10-7 up
Answer: _____
2. A proton (charge 1.6*10-19C and mass 1.67*10-27 kg) is moving with a
velocity v = 2*105 m/s in the positive z direction. A magnetic field of
B = 1.25*10-1 T is pointing in the positive y direction. Find the
magnitude and direction of the force acting on the proton.
a. 4*10-15 N, in the positive x-direction
b. 4*10-15 N, in the negative x-direction
c. 1.6*10-19 N, in the positive z-direction
d. 1.6*10-19 N, in the negative z-direction
Answer: _____
3. The magnetic force experienced by a moving charged particle depends
upon _____________.
1. the particle's charge
2. the particle's velocity
3. the magnetic field strength
a. 3 only
b. 1 and 2 only
c. 1 and 3 only
d. 2 and 3 only
e. 1, 2, and 3
Answer: _____
4. Two parallel long, straight wires are 0.004 m apart and carry
currents of 5.0 A and 10 A, respectively. Determine the net magnetic
field midway between the wires. Take B as positive if it is going into
the page.
a. -5.0*10-4 T
b. 5.0*10-4 T
c. -1.0*10-3 T
d. 1.0*10-3 T
Answer: _____
5. What is the strength of a magnetic field produced at a distance of
0.05 m from a 100 m long wire carrying a current of 4.0 A?
a. 4.0*10-5 T
b. 2.0*10-5 T
c. 1.6*10-5 T
d. 1.0*10-5 T
Answer: _____
6. A straight wire with a current placed in a uniform magnetic field
experiences a force that is ______________.
a. perpendicular to the current
b. perpendicular to the field
c. proportional to the size of the current
d. all of these
Answer: _____
7. The magnetic force on a charged particle moving in a magnetic field
_______________.
a. is zero if the particle moves perpendicular to the field
b. is a maximum if the particle moves parallel to the field
c. acts in the direction of motion for a positively charged particle
d. depends on the component of the particle's velocity that is perpendicular to the field
Answer: _____
8. The path of a charged particle moving in a plane perpendicular to a
uniform magnetic field _______________.
a. is a straight line
b. is a circle
c. is a parabola
d. not enough information
Answer: _____
9. Two long, parallel wires with currents are placed in a uniform
magnetic field. If the current in one wire is doubled and the current
in the other wire is halved, what happens to the magnitude of the force
between these two wires?
a. It is doubled.
b. It stays the same.
c. It is tripled.
d. It is quadrupled.
Answer: _____
10. A 1.0-m long wire is placed perpendicular to a magnetic field of
strength 0.20 T. If the wire experiences a force of 0.60 N, what is the
magnitude of the current moving through the wire?
a. 2.0 A
b. 1.0 A
c. 3.0 A
d. 4.0 A
Answer: _____
11. A long, straight wire carries a current of 5.0 A. At what distance
from the wire is its magnetic field 5.0*10-5 T?
a. 0.020 m
b. 0.20 m
c. 2.0 m
d. 20 m
Answer: _____