fringing effect

It  may be noted that  the  useful flux  while crossing air gap tend's  to bulge  out words as  shown lines  at b;b"  there by increasing  the effective area  of  the gap and  reducing  the flux density  in the air gap this effect is known  as fringing effect 

stroboscopic effect

In any type of discharge lamp the discharge  is actually extinguished twice per cycle and 100  time per second  in 50 hrz 50  these  is a sliaght stroboscopic effect ,the  effect makes  a revolving wheel appear to stand still [or] backward [or] a moving object to appear in a slow 

MAGNETIC HYSTERESIS

magnetic hysteresis
the phenomenon of lagging of flux density   B behind magnetizing  force H in the magnetic material's  subjected to cycle  of magnetization   is known as  magnetic hysteresis

B-h curve and hysteresis

The relation between the magnetic flux density  [B]  and the magnetic force  [h]  is called B-H curve    [or]  magnetizing curve

magnetic leakage[or]leakage

The magnetic flux that does not follow the desired path in magnetic circuit is called leakage flux

thus the ratio of total flux to the useful flux  is known  as leakage co- efficient [lamda]
Leakage flux co-efficient =total flux / useful flux

series magnetic circuit

A  magnetic circuit has a number of part of different materials carrying   the  same magnetic field [or] flux is called a series magnetic circuit  it is also called composite magnetic circuit.

magnetic circuit

  magnetic circuit                                                                                                                                                       The complete closed path followed by the magnetic lines  of force is  called a magnetic circuit