SOLUTIONS, Assignment 23
28.40.
I
DENTIFY
:
0
0
μ NI
Bμ nI
L
=
=
S
ET
U
P
:
0.150 m
L
=
E
XECUTE
:
0
(600) (8.00 A)
0.0402 T
(0.150 m)
μ
B
=
=
E
VALUATE
:
The field near the center of the solenoid is independent of the radius of the solenoid, as
long as the radius is much less than the length.
28.41.
(a) I
DENTIFY
and
S
ET
U
P
:
The magnetic field near the center of a long solenoid is given by Eq.(28.23),
0
.
B
nI
μ
=
E
XECUTE
:
Turns per unit length
7
0
0.0270 T
1790
(4
10 T m/A)(12.0 A)
B
n
I
π

=
=
=
×
⋅
turns/m
(b)
(1790 turns/m)(0.400 m)
716 turns
N
nL
=
=
=
Each turn of radius
R
has a length 2
R
of wire. The total length of wire required is
2
(2
)
(716)(2 )(1.40 10 m)
63.0 m.
N
R

=
×
=
E
VALUATE
:
A large length of wire is required. Due to the length of wire the solenoid will have
appreciable resistance.
28.44.
I
DENTIFY
:
Example 28.10 shows that outside a toroidal solenoid there is no magnetic field and inside it
the magnetic field is given by
0
.
2
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 Fall '10
 dfs
 Magnetic Field, EXECUTE

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