PS08-1
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
Department of Physics
8.02
Fall 2008
Label with your name, table number and group. Turn in at the homework box.
Problem Set 8
Due: Thursday, October 30
th
at 12:00 pm
Warm Up
Problem 1: Charges in a Uniform Field
An electron with velocity
ˆ
ˆ
x
y
v
v
+
i
j
moves through a uniform magnetic field
ˆ
ˆ
x
y
B
B
+
i
j
(a)
Find the magnitude of the force on the electron.
(b)
Repeat your calculation for a proton having the same velocity.
Problem 2: Power Line
A horizontal power line carries a current of
I
from south to north. Earth's magnetic field
(
B
Earth
= 62.1 μT) is directed toward the north and is inclined downward at an angle
θ
to
the horizontal. Find the magnitude of the magnetic force on a length
L
of the line due to
Earth's field.
Please also calculate a value numerically for
I
= 2000 A,
θ
= 73.0º and
L
=
100 m, since it’s useful to think about real world numbers.
Problem 3: Triangular Loop
A current loop, carrying a current
I
, is in the shape of a right triangle with sides 3, 4, and
5 cm. The loop is in a uniform magnetic field
B
whose direction is parallel to the current
in the 5 cm side of the loop.
Find the magnitude of
(a)
the magnetic dipole moment of the loop in amperes-square meters; and
(b)
the torque on the loop.

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