63. (a) We are given
~
B
=
B
x
ˆ
i=6
×
10
−
5
ˆ
iT
,sothat
~v
×
~
B
=
−
v
y
B
x
ˆ
kwhere
v
y
=4
×
10
4
m/s. We note
that the magnetic force on the electron is (
−
e
)(
−
v
y
B
x
ˆ
k) and therefore points in the +
ˆ
k direction,
at the instant the electron enters the FeldFlled region. In these terms, Eq. 2916 becomes
r
=
m
e
v
y
eB
x
=0
.
0038 m
.
(b) One revolution takes
T
=2
πr/v
y
=0
.
60
µ
s, and during that time the “drift” of the electron in the
x
direction (which is the
pitch
of the helix) is ∆
x
=
v
x
T
=0
.
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This note was uploaded on 11/12/2011 for the course PHYS 2001 taught by Professor Sprunger during the Fall '08 term at LSU.
 Fall '08
 SPRUNGER
 Physics, Force

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