Page 504 - Basic Electrical Engineering

Example 5.3 A rectangular shape iron core has an air gap of 0.01 cm. The
mean length of the flux path through iron is 39.99 cm. The relative
permeability of iron is 2000. The coil has 1000 turns. The cross-sectional

2
area of the core is 9 cm . Calculate the current required to produce a flux of 1
mWb in the core.

Solution:

Total reluctance of the flux path = Reluctance of iron path + Reluctance of air
gap,

i.e.,

Note: the iron path permeability is m which is equal to μ μ whereas for the
0 r
air gap the permeability is μ only.
0

Figure 5.22

Substituting the given values,