Shie, Gary – Homework 23 – Due: Oct 27 2004, 4:00 am – Inst: Turner
1
This
printout
should
have
11
questions.
Multiplechoice questions may continue on
the next column or page – find all choices
before answering.
The due time is Central
time.
001
(part 1 of 2) 10 points
Given:
μ
0
= 1
.
25664
×
10

6
N
/
A
2
.
A solenoid has 150 turns of wire uniformly
wrapped around an airfilled core, which has a
diameter of 11
.
9 mm and a length of 6
.
55 cm.
Calculate
the
selfinductance
of
the
solenoid.
Correct answer: 4
.
80104
×
10

5
H.
Explanation:
Given:
The number of turns in the solenoid
N
= 150 turns, the diameter of the solenoid
D
= 11
.
9 mm, and the length of the solenoid
l
= 6
.
55 cm.
The selfinductance of a solenoid is given
by
L
1
=
N
Φ
I
,
where Φ is the total flux inside the solenoid
and
I
is the current in the wire wrapped
around the solenoid.
From the text we can use Ampere’s Law to
find that the magnetic field in the solenoid is
B
=
μ
0
N I
‘
,
where
μ
=
μ
0
is the magnetic permeability of
the air core which is the same as free space.
The magnetic flux in the solenoid is
Φ =
B A
=
B π D
2
4
.
Using the above expressions for Φ and
B
,
we obtain for the inductance of the solenoid
L
1
=
N B A
I
=
μ
0
N
2
π D
2
4
‘
= (1
.
25664
×
10

6
N
/
A
2
) (150)
2
×
π
(0
.
0119 m)
2
4 (0
.
0655 m)
= 4
.
80104
×
10

5
H
.
002
(part 2 of 2) 10 points
The core is replaced with a soft iron rod that
has the same dimensions, but a magnetic per
meability 800
μ
0
.
What is the new inductance?
Correct answer: 0
.
0384083 H.
Explanation:
Let
L
2
be the inductance of the solenoid
with the soft iron core.
In the first part of
the problem we just need to change
μ
0
by
μ
.
Thus
L
2
=
μ N
2
π D
2
4
‘
=
μ
μ
0
L
1
= 800 (4
.
80104
×
10

5
H)
= 0
.
0384083 H
.
003
(part 1 of 1) 10 points
A 3
.
2 H inductor carries a steady current
of 0
.
595 A. When the switch in the circuit is
thrown open, the current disappears in 7
.
3 ms.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview.
Sign up
to
access the rest of the document.
 Spring '10
 ERSKINE
 Physics, Work, Magnetic Field, Correct Answer, Inductor, shie

Click to edit the document details