# Magnetic force will develop stress in the core ,

Magnetic circuits and cores lossesCore loss = Hysuresis loss + Eddy current lossPcore =Kn f B­nmax+Kc f2B2maxit is rather easier to measure the core loss with the help of a wattmeter.the wattmetter readings corresponding to three differents applied voltages and frequencies like Kc ,Kn and Nthe point lies in the linear zone of the B.H charecteristics in order to get a constant value of the inductance.|Naturelly there will be force of attraction Fa between the forces.Expect for the facr that this force will develop stress in the core , no physical movement is possible as the structure is rigid.A linear magnetic circuit has a mean flux length of 100 cm and uniform cross sectional area of 25 cm2.The energy stored in the air gap. Force acting between the forces of the cores accross the gap to the same coil current.The magnetic circuits and core losses is subjected to time varying field. We first must know the origin of these two losses.If at any time flux is increasing with time in the upword direction d?/dt is postive and e12 will come out to negtive as well as the time.On the other hand,at any time flux is decreasing with time in the upword direction d?/dt is negtive and e12 will come out to be postive as well as the time.Without any loss of generaly,oe may consider thisto be a part of a magnetic circuit.It is imporatant to note here that to calculate induced voltage in the path, the value of flux to be taken is the flux enclosed by the path. ?max =Bmax x area of the loopEddy current will therefore cause a power lose heating to the core.Concllusion is that solid black of iron should not be used to construct the core when exciting current will be AC.To drive on expression for the eddy current loss, we shall first calculate the power loss in the elements strip and then integrate suitably to far total loss.Also it is inversaly propectional to the resistivity of the material . The flux too naturally wiill be function of time and cause induced voltage e12 in the coil with a polarity to oppose the increase of inflow of current as shown.Therefore during the interval when it is increasing the coil absorbs energy .It is to know how much energy does the coil absorb when current is increasing flux o to 10?the material with us.This lock of retracing same path of the curve is called Hysteresis.Obiviosly energy absorbed during rising current is more than the energy returned during lowring of current.Magnetic circuit with a core of fermagnetic material , volume and thickness of the plates are constant and the total core loss less can be expresses as follows.