Page 498 - Basic Electrical Engineering

Electric Circuit Magnetic Circuit
Current, I Flux, ϕ

EMF, V MMF, N I

Resistance, R Reluctance, S

Electric field intensity = Magnetic field intensity,

5.7 MAGNETIC LEAKAGE AND FRINGING

Let us consider a magnetic circuit as in Fig. 5.17 (a). The current passing
through the winding produces flux which is distributed equally on both sides

of the coil as shown.
As shown in Fig. 5.17 (b), most of the flux will flow or pass through the
magnetic material which is called the main flux or useful flux. However, a

certain percentage of flux will link the coil itself and will not pass through the
entire core. This flux is called leakage flux. Leakage flux completes its path

through air instead of going through the entire iron path.
In a magnetic circuit with some air gap, when flux has to pass through the

air gap, there is tendency of the magnetic flux to spread out at the two edges
or sides. This effect is called fringing.