Magnitude of a magnetic field
1. A proton traveling at a speed of 3.5 x 106 rn/s passes perpendicular to a
uniform magnetic field of 42 x iO_2 T What is the magnitude of the
force on the proton while the proton is in the magnetic field?
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2. A uniform 1.5 T magnetic field points north. If an electron moves verti
cally downward (toward the ground) with a speed of 25 x
m/s
through this field, what force (magnitude and direction) will act on it?
3. A proton moves straight upward (away from the ground) through a uni
form magnetic field that points from east to west and has a magnitude of
2.5 T. If the proton moves with a speed of 1.5 x
rn/s through this
field, what force (magnitude and direction) will act on it?
4. A proton traveling to the right along the x-axis enters a region where
there is a magnetic field of magnitude 2 5 T directed upward along the
y-axis. If the proton experiences a force of 3.2 x 1012 N, find the speed
of the proton.
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If an electron m an electron beam experiences a force of 2 0 x l0_14 N
down while traveling north at a speed of 1.5 x 106 m/s, then what is the
magnitude and direction of the magnetic field that deflects the electron?
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6. An alpha particle (the nucleus of a helium atom, carrying a charge of
3 2 x 10 —19 C) moves at 5 5 x 10 7 rn/s at a right angle to a magnetic field
If the particle experiences a force of 1.5 x i’ N due to the magnetic
field, then what is the magnitude of the magnetic field?
.
Force on a currentcarryiflg conductor
in Sample Problem 21R if ti e direction of the current
1. What is
points west to east?
2
A wire 1 0 m long experiences a magnetic force of 050 N due to a perpendicular uniform magnetic field. If the wire carries a current of 10.0 A,
what is the magnitude of the magnetic field?•
3. The magnetic force acting on a wire that is perpendicular to a 1.5 T uniform magnetic field is 4.4 N. If the current in the wire is 5.0 A, what is
the length of the wire that is inside the magnetic field?
4. A 2.5 N magnetic force acts on a 475 m wire that is perpendicular to a
0.50 T magnetic field. What is the current in the wire?
5. The magnetic force on a straight 0.15 m segment of wire carrying a cur
rent of 4.5 A is 1.0 N. What is the magnitude of the component of the
magnetic field that is perpendicular to the wire?
a region
19 Two charged particles are projected into
perpendicula
r to
where there is a magnetic field
their velocities If the particles are deflected in
them?
opposite directions what can you say about
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22. A proton moving horizontally enters a region where
there is a uniform magnetic field perpendicular to the
proton’s velocity as shown in Figure 21-18. Describe
the proton’s subsequent motion. How would an elec
tron behave under the same circumstances?
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through each magnetic field in Figure 21-19.
(See Sample Problem 21A.)
.
a.
Figure 21-18
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38. A proton moves eastward in the plane of Earth’s mag
netic equator so that its distance from the ground
remains constant. What is the speed of the proton if
Earth’s magnetic field points north and has a magni
T?
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45. A singly charged positive ion with a mass of 6.68 x
kg moves clockwise with a speed of 1.00 x
rn/s in a circular path with a radius of 3.00 cm.
Find the direction and strength of the magnetic
field. (Hint: The magnetic force exerted on the ion
is the force that maintains circular motion, and the
speed of the ion given is its tangential speed.)
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b.
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37. A thl i:ooong copper rod has a mass of 50.0j.
What is the minimum current needed in the rod to
cause it to float in a magnetic field of 2.00 T?
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31. Find the direction of the force on a proton
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p
29. A duck flying due east at 15 m/s passes ovvri4tJa
where the magnetic field of the Earth is 5.0
directed north. The duck has a positive
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4.0 x 10—8 C. What is the magnetic forcc
the duck?
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Figure 21-19
40. A proton travels with a speed of 3.0 x 106 rn/s at
an angle of 370 west of north. A magnetic field of
0.30 T points to the north. Determine the following:
a. the magnitude of the magnetic force on the
proton
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b. the direction of the magitic force on the
proton
c. the proton’s acceleration
(Hint: the magnetic force is proportional to the
component of the proton’s velocity that is perpen
dicular to the magnetic field.)