ECE 3070 Sample Exam #1 Problems
1.
A magnetic circuit has the following dimensions:
A = 16 cm
2
, length = 40 cm, and N = 360 turns.
The relative permeability of the core is μ
r
= 50,000.
For a magnetic flux density of 1.5 T in the
core, determine,
(a)
The flux, ø.
(0.0024 Wb)
(b)
The total flux linkage of the coil.
(0.864 V•sec)
(c)
The required current in the coil.
(0.026 A)
2.
Consider the magnetic structure shown below. All dimensions are given in centimeters.
The
permeability of the core material can be considered to be infinity, i.e., μ
r
= 8.
The stacking factor
for the core is known to be 0.95.
(a)
Find the value of h required so that the magnetic flux is the same in both air gaps.
(16.66 cm)
(b)
If h=20 cm, and the current in the coil is 20 Amps, find the energy stored in the magnetic field
associated with the coil.
(140 J)
10
125
15
10
35
10
h
12
15
50
5
Thickness = 8 cm.
N= 1000
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 Spring '09
 Harley
 Magnetism, Flux, Magnetic Field, flux density, total flux linkage

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