Introductory Physics Volume Two

94 Magnetic Fields 4.7
in the positive z direction. If the electric field has a strength of 20N/C
in the positive z direction, what is the magnetic field in the region?
⊲ Problem 4.10
A duck flying due north at 15 m s
passes over Atlanta, where the Earth’s
magnetic field is 5.0 × 10 −5 T in a direction 60 ◦ below the horizontal
line running north and south. If the duck has a net positive charge of
0.040µC, what is the magnetic force acting on it?
⊲ Problem 4.11
A proton moves with a velocity of v = (2î − 4ĵ + ˆk) m s
in a region in
which the magnetic field is B ⃗ = (î + 2ĵ − 3ˆk)T. What is the magnitude
of the magnetic force this charge experiences?
⊲ Problem 4.12
Show that the work done by the magnetic force on a charged particle
moving in a magnetic field is zero for any displacement of the particle.
⊲ Problem 4.13
Below is shown a cube (40cm on each edge) in a magnetic field with a
wire carrying a current I = 5.0A over the surface of the cube. If there
is a magnetic field B ⃗ = 0.020Tĵ. What is the magnitude and direction
of the magnetic force on each straight segment of the current loop?
y
B
d
a
I
z
c
b
x
⊲ Problem 4.14
A singly charged positive ion has a mass of 3.20×10 −26 kg. After being
accelerated through a potential difference of 833V, the ion enters a
magnetic field of 0.920T along a direction perpendicular to the direction
of the field. Calculate the radius of the path of the ion in the field.
Find the velocity of the particle first then use the circular motion
result.
⊲ Problem 4.15
A proton (charge +e, mass m p ), a deuteron (charge +e, mass 2m p ),
and an alpha particle, (charge +2e, mass 4m p ) are accelerated through
a common potential difference, V . The particles enter a uniform magnetic
field B, in a direction perpendicular to B. The particles move in