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EE321.
Final Exam
Spring 2004
Name:
Student ID:
Instructions:
Work ALL Problems.
Show your work.
Each problem is worth 25 pts.
There was a physics student named bright.
He thought a lot about light.
He went out one day in the usual way
and came back the previous night.
– Garrison Keillor
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View Full DocumentProblem 1 – MEC Modeling
Starting with the definition of flux, and the definition of MMF drop, derive Ohm’s law for linear magnetic
material.
In particular, show that
Φ
=
R
F
b
a
,
, where
( )
A
l
R
µ
/
=
where
b
a
F
,
is the MMF drop from node a to node
b,
R
is reluctance,
Φ
is the flux into node A,
l
is the length from node a to node b,
A
is the cross sectional area
of the path,
and
is the absolute permeability.
Problem 2 – Energy Conversion
Consider a magnetic system with the following flux linkage equations
2
1
2
2
1
1
4
3
5
i
i
i
i
+
=
+
=
λ
Initially, both currents are zero.
If first winding 1 is energized to 1 A, and then winding 2 is energized from 0
to 2 A, what is the coenergy?
Now, consider the situation if winding 1 goes from 0 to 1 A (linearly in time)
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 Spring '08
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