magnetic hysteresis loop.The different between them is the value of coercive force. Ferromagnet with strong coercive force is called hard magnetic material,and if its coercive force is a small one,we call it soft magnetic material. 3.Observe the hysteresis loop through the oscilloscope. Figure 4 is the circuit diagram to observe the magnetic hysteresis loop through the oscilloscope This experiment is to investigate a ferrite magnetic core.This sample has an average magnetic path of L and the turns of primary coils is Ni.If the exciting current is i,according to Ampere circuital theorem,among the sample we have 0+ CH2 signal source 8= R CHI 0+ Fig.4 The circuit diagram to observe the magnetic hysteresis loop through the oscilloscope HL=N i (2) Then the input voltage of the x axis of oscilloscope is U&,=Ri=- LH (3) where R,L and N are constant,which indicate URi is proportional to the magnetic field H. Suppose the sectional area of the magnetic core is S,according to the law of electromagnetic induction,in the secondary coil with turns of N2,the induced electromotive force should be E:=-N,s dB dt (4) Considering the turns of secondary coil N2 is small,self induction electromotive force can be ignored.We choose a suitable value of Rand Cin the circuit to get Rthen 3- - 3 magnetic hysteresis loop. The different between them is the value of coercive force. Ferromagnet with strong coercive force is called hard magnetic material, and if its coercive force is a small one, we call it soft magnetic material. 3．Observe the hysteresis loop through the oscilloscope. Figure 4 is the circuit diagram to observe the magnetic hysteresis loop through the oscilloscope. This experiment is to investigate a ferrite magnetic core. This sample has an average magnetic path of L and the turns of primary coils is N1. If the exciting current is i1，according to Ampere circuital theorem, among the sample we have 1 1 HL = N i （2） Then the input voltage of the x axis of oscilloscope is H N R L U R i R 1 1 1 1 1 = = （3） where R1, L and N1 are constant, which indicate UR1 is proportional to the magnetic field H. Suppose the sectional area of the magnetic core is S，according to the law of electromagnetic induction, in the secondary coil with turns of N2, the induced electromotive force should be t B N S d d 2 = − 2 ε （4） Considering the turns of secondary coil N2 is small，self induction electromotive force can be ignored. We choose a suitable value of R2 and C in the circuit to get Rଶ ب 1 ωC ൗ ，then Fig. 4 The circuit diagram to observe the magnetic hysteresis loop through the oscilloscope