Kapoor (mk9499) – homework26 – Turner – (60230)
1
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12
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001
(part 1 of 3) 10.0 points
A metal strip 2 cm wide and 0
.
15 cm thick
carries a current of 30 A in a uniform magnetic
field of 1 T. The Hall voltage is measured to
be 4
.
32
μ
V.
The charge on an electron is 1
.
6
×
10

19
C.
vector
B
2 cm
0
.
15 cm
I
a
b
Calculate the drift velocity of the electrons
in the strip.
Correct answer: 0
.
216 mm
/
s.
Explanation:
Let :
V
H
= 4
.
32
μ
V = 4
.
32
×
10

6
V
,
B
= 1 T
,
and
w
= 2 cm = 0
.
02 m
.
The Hall voltage as a function of the drift
velocity of the electrons in the strip is
V
H
=
v
d
B w ,
so
v
d
=
V
H
B w
=
4
.
32
×
10

6
V
(1 T) (0
.
02 m)
·
10
3
mm
1 m
=
0
.
216 mm
/
s
.
002
(part 2 of 3) 10.0 points
The charge on the electron is 1
.
6
×
10

19
C.
Find the number density of the charge car
riers in the strip.
Correct answer: 2
.
89352
×
10
28
m

3
.
Explanation:
Let :
I
= 30 A
,
t
= 0
.
15 cm = 0
.
0015 m
,
and
q
= 1
.
6
×
10

19
C
.
The current is
I
=
n A q v
d
n
=
I
A q v
d
=
I
w t q v
d
=
30 A
(0
.
02 m) (0
.
0015 m)
×
1
(1
.
6
×
10

19
C) (0
.
000216 m
/
s)
=
2
.
89352
×
10
28
m

3
.
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 Fall '08
 Turner
 Physics, Work, Magnetic Field, Correct Answer, Kapoor

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