Experiment 3.8. Magnetization Curve and Hysteresis LoopofTheFerromagneticMaterialFerromagnetic materials are the materials that exhibit the tendency of magnetizationfor a short time even after the removal of an external magnetic field. This property iscalled hysteresis. Among all types of magnetic materials, ferromagnetic materials arestrongly attracted to magnetic fields. Such materials have a spontaneous netmagnetization at the atomic level, even when no external magnetic field is present.Most of the ferromagnetic materials are metals. Common examples of ferromagneticsubstances are Iron, Cobalt, Nickel, etc. Besides, metallic alloys and rare earthmagnets are also classified as ferromagnetic materials. Magnetite is a ferromagneticmaterial which is formed by the oxidation of iron into an oxide. It has a Curietemperature of 580°C. Magnetite has the greatest magnetism among all the naturalminerals on the Earth. There are wide applications of ferromagnetic materials in theindustry.They are widely used in devices like electric motors, generators,transformers, telephones, loudspeakers, and magnetic stripes on the back of creditcards.Experimental Objectives(1) Understand the fundamental concepts of magnetization curve, hysteresis loop,permeability,coerciveforce,andresidualmagnetism(2) Learn how to observe magnetization curve and hysteresis loop of a ferromagneticmaterial using an oscilloscope.(3) Measure permeability, saturation flux density, coercive force, and residualmagnetism.(4) Compare the hysteresis loops under different frequencies for differentferromagnetic materials.Experimental InstrumentsDH4516N apparatus of measuring magnetic hysteresis loop,digital oscilloscopeExperimentalPrinciples
Experiment 3.8. Magnetization Curve and Hysteresis Loop of The Ferromagnetic Material Ferromagnetic materials are the materials that exhibit the tendency of magnetization for a short time even after the removal of an external magnetic field. This property is called hysteresis. Among all types of magnetic materials, ferromagnetic materials are strongly attracted to magnetic fields. Such materials have a spontaneous net magnetization at the atomic level, even when no external magnetic field is present. Most of the ferromagnetic materials are metals. Common examples of ferromagnetic substances are Iron, Cobalt, Nickel, etc. Besides, metallic alloys and rare earth magnets are also classified as ferromagnetic materials. Magnetite is a ferromagnetic material which is formed by the oxidation of iron into an oxide. It has a Curie temperature of 580°C. Magnetite has the greatest magnetism among all the natural minerals on the Earth. There are wide applications of ferromagnetic materials in the industry. They are widely used in devices like electric motors, generators, transformers, telephones, loudspeakers, and magnetic stripes on the back of credit cards. Experimental Objectives (1) Understand the fundamental concepts of magnetization curve, hysteresis loop, permeability, coercive force, and residual magnetism. (2) Learn how to observe magnetization curve and hysteresis loop of a ferromagnetic material using an oscilloscope. (3) Measure permeability, saturation flux density, coercive force, and residual magnetism. (4) Compare the hysteresis loops under different frequencies for different ferromagnetic materials. Experimental Instruments DH4516N apparatus of measuring magnetic hysteresis loop, digital oscilloscope Experimental Principles
Causes ofFerromagnetismIn a ferromagnetic material in the unmagnetized state, atomic dipoles in small regionscalled domains are aligned in the same direction.The domains exhibit a net magneticmoment even in the absence of an external magnetizing field. However, the magneticmoments of neighboring domains are oriented in opposite directions. They cancel out,and therefore the net magnetic moment of the material is zero. On applying anexternal magnetic field, these domains align themselves in the direction of the appliedfield. In this way, the material is strongly magnetized in a direction parallel to themagnetizing field producing a strong magnetic effect.DBYJU'SV兴1A.RandomdomainorientatiorB.AftermagnetizationFigure3.8-1.causesofferromagnetismMagnetizationorB-HCurveFor ferromagnetic materials, the relationship between the flux density, B and themagnetic field strength, H can be defined by the fact that the permeability, μ is not aconstant but a function of the magnetic field intensity thereby giving magnetic fluxdensity as: B = μH = μou,H. The relative permeability, symbol μr was defined asthe ratio of the absolute permeability μand the permeability of free space μo (avacuum, μo=4π ×10-7T·m/A).When the magnetic material is totallydemagnetizedand isthensubjectedtogradually increasingmagnetizingforce,thenthemagneticfluxdensityinthematerial will be increased byalargerfactorasa resultof its relative permeability for the material compared to the magnetic flux density invacuum. By plotting values of flux density, B against the field strength, H we canproduce magnetization curvefor each type of core material used as shown below
Causes of Ferromagnetism In a ferromagnetic material in the unmagnetized state, atomic dipoles in small regions called domains are aligned in the same direction. The domains exhibit a net magnetic moment even in the absence of an external magnetizing field. However, the magnetic moments of neighboring domains are oriented in opposite directions. They cancel out, and therefore the net magnetic moment of the material is zero. On applying an external magnetic field, these domains align themselves in the direction of the applied field. In this way, the material is strongly magnetized in a direction parallel to the magnetizing field producing a strong magnetic effect. Figure 3.8-1. causes of ferromagnetism Magnetization or B-H Curve For ferromagnetic materials, the relationship between the flux density, B and the magnetic field strength, H can be defined by the fact that the permeability, μ is not a constant but a function of the magnetic field intensity thereby giving magnetic flux density as: 𝐵 = 𝜇𝐻 = 𝜇0𝜇𝑟𝐻. The relative permeability, symbol μr was defined as the ratio of the absolute permeability μ and the permeability of free space μ0 (a vacuum, 𝜇0 = 4𝜋 × 10−7 T ∙ m/A ). When the magnetic material is totally demagnetized and is then subjected to gradually increasing magnetizing force, then the magnetic flux density in the material will be increased by a larger factor as a result of its relative permeability for the material compared to the magnetic flux density in vacuum. By plotting values of flux density, B against the field strength, H we can produce magnetization curve for each type of core material used as shown below
2.01.8B-HCurvesfor Various MetalsSteel1.61.41.2MagneticSaturationg-1.0su0.8Iron0.6IE0.4Air0.210002000300040005000600070008000900010000MagneticFieldStrength-H(At/m)Figure 3.8-2. magnetization curves for air, iron and steelThe set of magnetization curves represents an example of the relationshipbetween B and H for soft-iron and steel cores but every type of core material will haveits own set of magnetic hysteresis curves. You may have noticed that the flux densityincreases in proportion to the field strength until it reaches a certain value where itcannot increase any more becoming almost level and constant even though the fieldstrength continues to increase. The point on the graph where the flux density reachesits limit is called Magnetic Saturation. As the magnetic field strength, H increasesthese molecular magnets become more and more aligned until they reach perfectalignment producing maximum flux density and any increase in the magnetic fieldstrength due to an increase in the electrical current flowing through the coil will havelittleornoeffect.PermeabilityIn magnetics, permeability is the ability of a material to conduct flux. The magnitudeof the permeability at a given induction is the measure of the ease with which a corematerial can be magnetized to that induction. As presented above, it is defined as theratio of the flux density, B, to the magnetizing force, H. The slope of themagnetization curve, at any given point gives the permeability at that point.Permeability can be plotted against a typical B-H curve, as shown in Figure 3.8-3.Permeability is not constant; therefore, its value can be stated only at a given value ofB or H
Figure 3.8-2. magnetization curves for air, iron and steel The set of magnetization curves represents an example of the relationship between B and H for soft-iron and steel cores but every type of core material will have its own set of magnetic hysteresis curves. You may have noticed that the flux density increases in proportion to the field strength until it reaches a certain value where it cannot increase any more becoming almost level and constant even though the field strength continues to increase. The point on the graph where the flux density reaches its limit is called Magnetic Saturation. As the magnetic field strength, H increases these molecular magnets become more and more aligned until they reach perfect alignment producing maximum flux density and any increase in the magnetic field strength due to an increase in the electrical current flowing through the coil will have little or no effect. Permeability In magnetics, permeability is the ability of a material to conduct flux. The magnitude of the permeability at a given induction is the measure of the ease with which a core material can be magnetized to that induction. As presented above, it is defined as the ratio of the flux density, B, to the magnetizing force, H. The slope of the magnetization curve, at any given point gives the permeability at that point. Permeability can be plotted against a typical B-H curve, as shown in Figure 3.8-3. Permeability is not constant; therefore, its value can be stated only at a given value of B or H
B, μrABB-HA,-Hu0H,HFigure3.8-3.variation of relative permeability,μr along the magnetizing curve.RetentivityLet's assume that the ferromagnetic core material has reached its saturation point,maximum flux density.If we remove the magnetizing current flowing through the coilwe would expect the magnetic field around the coil to disappear as the magnetic fluxreduced to zero.However, the magnetic flux does not completely disappear as theelectromagnetic core material still retains some of its magnetism even when thecurrent has stopped flowing in the coil. This ability for a coil to retain some of itsmagnetism within the core after the magnetization process has stopped iscalled retentivity or remanence, while the amount of flux density still remaining in thecore is called Residual Magnetism, Br.The reason for this that some of the tiny molecular magnets do not return to acompletely random pattern and still point in the direction of the original magnetizingfield giving them a sort of “memory" Some ferromagnetic materials have a highretentivity (magnetically hard) making them excellent for producing permanentmagnets.While other ferromagnetic materials have low retentivity (magnetically soft)making them ideal for use in electromagnets, solenoids or relays. One way to reducethis residual flux density to zero is by reversing the direction of the current flowingthrough the coil, thereby making the value of H, the magnetic field strength negative.This effect is called a Coercive Force, He
Figure 3.8-3. variation of relative permeability, μr along the magnetizing curve. Retentivity Let’s assume that the ferromagnetic core material has reached its saturation point, maximum flux density. If we remove the magnetizing current flowing through the coil we would expect the magnetic field around the coil to disappear as the magnetic flux reduced to zero. However, the magnetic flux does not completely disappear as the electromagnetic core material still retains some of its magnetism even when the current has stopped flowing in the coil. This ability for a coil to retain some of its magnetism within the core after the magnetization process has stopped is called retentivity or remanence, while the amount of flux density still remaining in the core is called Residual Magnetism, Br. The reason for this that some of the tiny molecular magnets do not return to a completely random pattern and still point in the direction of the original magnetizing field giving them a sort of “memory”. Some ferromagnetic materials have a high retentivity (magnetically hard) making them excellent for producing permanent magnets. While other ferromagnetic materials have low retentivity (magnetically soft) making them ideal for use in electromagnets, solenoids or relays. One way to reduce this residual flux density to zero is by reversing the direction of the current flowing through the coil, thereby making the value of H, the magnetic field strength negative. This effect is called a Coercive Force, Hc
MagneticHysteresis LoopB B,B-H-HHH,H-B.BFigure3.8-4.magnetic hysteresis loopThe Figure 3.8-4 shows the behavior of a ferromagnetic core graphically as therelationship between B and His non-linear. Starting with an unmagnetized corebothB and Hwill beat zero,point Oonthemagnetization curve.Ifthemagnetizationcurrent, iis increased in a positive direction to some value the magnetic fieldstrength H increases linearly with i and the flux density B will also increase as shownby the curve from point O to point a as it heads towards saturation.Now if the magnetizing current in the coil is reduced to zero, the magnetic fieldcirculating around the core also reduces to zero. However, the coils magnetic flux willnot reach zero due to the residual magnetism present within the core and this isshown on the curve from point a to point b. To reduce the flux density at point b tozero we need to reverse the current flowing through the coil. The coercive forcereverses the magnetic field re-arranging the molecular magnets until the core becomesunmagnetized at point c. An increase in this reverse current causes the core to bemagnetized in the opposite direction and increasing this magnetization current furtherwill cause the core to reach its saturation point but in the opposite direction,point d on the curve. This point is symmetrical to point b. If the magnetizing current isreduced again to zero the residual magnetism present in the core will be equal to theprevious value but in reverse at point e. Again reversing the magnetizing currentflowing through the coil this time into a positive direction will cause the magneticfluxto reach zero,pointfonthe curve and as beforeincreasing the magnetizationcurrent further in a positive direction will cause the core to reach saturation at point a
Magnetic Hysteresis Loop Figure 3.8-4. magnetic hysteresis loop The Figure 3.8-4 shows the behavior of a ferromagnetic core graphically as the relationship between B and H is non-linear. Starting with an unmagnetized core both B and H will be at zero, point O on the magnetization curve. If the magnetization current, i is increased in a positive direction to some value the magnetic field strength H increases linearly with i and the flux density B will also increase as shown by the curve from point O to point a as it heads towards saturation. Now if the magnetizing current in the coil is reduced to zero, the magnetic field circulating around the core also reduces to zero. However, the coils magnetic flux will not reach zero due to the residual magnetism present within the core and this is shown on the curve from point a to point b. To reduce the flux density at point b to zero we need to reverse the current flowing through the coil. The coercive force reverses the magnetic field re-arranging the molecular magnets until the core becomes unmagnetized at point c. An increase in this reverse current causes the core to be magnetized in the opposite direction and increasing this magnetization current further will cause the core to reach its saturation point but in the opposite direction, point d on the curve. This point is symmetrical to point b. If the magnetizing current is reduced again to zero the residual magnetism present in the core will be equal to the previous value but in reverse at point e. Again reversing the magnetizing current flowing through the coil this time into a positive direction will cause the magnetic flux to reach zero, point f on the curve and as before increasing the magnetization current further in a positive direction will cause the core to reach saturation at point a
Then the B-Hcurve follows the path of a-b-c-d-e-f-a as the magnetizing currentflowing through the coil alternates between a positive and negative value such as thecycle of an AC voltage. This path is called a Magnetic Hysteresis Loop.Magnetic Hysteresis Loops for Soft and Hard MaterialsMagnetic hysteresis results in the dissipation of wasted energy in the form of heatwith the energy wasted being in proportion to the area of the magnetic hysteresis loop.Hysteresis losses will always be a problem in AC transformers where the current isconstantly changing direction and thus the magnetic poles in the core will cause lossesbecause they constantly reverse direction,Rotating coils in DC machines will alsoincur hysteresis losses as they are alternately passing north the south magnetic poles.There are twomajor classes of ferromagnetic materials:soft ferromagnets and hardferromagnets.Soft magnetic materials are characterized byvery small values of thecoercive force such as iron or silicon steel.They are easily magnetized anddemagnetized making them ideal for use in relays, solenoids and transformers. Hardmagnetic materials are characterized by large values of the coercive force and residualmagnetism, such as SmCo alloys, NdFeB alloys, and Strontium ferrites.OEVeOrCE"Hard"Ferromagnetic"Soft"FerromagneticMaterialMaterialFigure 3.8-5. magnetic hysteresis loops for soft and hard materialsPrincipleofahysteresismeasurementAs discussed above, the magnetic hysteresis loop reveals a lot of information abouttheproperties of corematerials used in coils andtransformers.Importantparametersassociated with the hysteresis loop are (1) the residual magnetism, Br,(2) the coerciveforce, He, and (3) the maximum relative permeability. This measurement can be donewith a digital oscilloscope.The circuit diagram is shown in Figure 3.8-6
Then the B-H curve follows the path of a-b-c-d-e-f-a as the magnetizing current flowing through the coil alternates between a positive and negative value such as the cycle of an AC voltage. This path is called a Magnetic Hysteresis Loop. Magnetic Hysteresis Loops for Soft and Hard Materials Magnetic hysteresis results in the dissipation of wasted energy in the form of heat with the energy wasted being in proportion to the area of the magnetic hysteresis loop. Hysteresis losses will always be a problem in AC transformers where the current is constantly changing direction and thus the magnetic poles in the core will cause losses because they constantly reverse direction. Rotating coils in DC machines will also incur hysteresis losses as they are alternately passing north the south magnetic poles. There are two major classes of ferromagnetic materials: soft ferromagnets and hard ferromagnets. Soft magnetic materials are characterized by very small values of the coercive force such as iron or silicon steel. They are easily magnetized and demagnetized making them ideal for use in relays, solenoids and transformers. Hard magnetic materials are characterized by large values of the coercive force and residual magnetism, such as SmCo alloys, NdFeB alloys, and Strontium ferrites. Figure 3.8-5. magnetic hysteresis loops for soft and hard materials Principle of a hysteresis measurement As discussed above, the magnetic hysteresis loop reveals a lot of information about the properties of core materials used in coils and transformers. Important parameters associated with the hysteresis loop are (1) the residual magnetism, Br , (2) the coercive force, Hc, and (3) the maximum relative permeability. This measurement can be done with a digital oscilloscope. The circuit diagram is shown in Figure 3.8-6
R1N.-CH26)CHI (x)Figure3.8-6.measuringarrangementwith adigital oscilloscopeThe core under test is provided with two windings. The first winding (the number ofturns N) is fed with an alternating current in (the angular frequency w), it will cause amagnetomotive force F.Dependently of the distance traveled by the magnetic fieldlines, the magnetic circuit length L, it results in a magnetic field strength:NiilH=LThen the partial voltage on the resistor Ri isLRIHUR,=i,R1:N1The second winding is used for measuring the induction B. The generatedelectromotive force in this winding is proportional to the flux change d within thecore. Because the flux density is equal to the product of the magnetic induction andthe cross sectional area of the core: = Bs, the relationship between the change ofinductionand electromotiveforce is:e2dtdB =N2SThe current iz,can be calculated:8212R2 +(/αCIf R2 >wc, then the voltage on the capacitor C isN2SQ1Uc =izdt=A--CCR2In the X-Y mode the field strength H(Ur,) is plotted on the X-axis, and the fluxdensity B (Uc) on the Y-axis. Adjust the scope settings so that the hysteresis loopappears on the center of theaxis and covers onefull period.If R2 < 1 /1/c, then the Uc-Ur.curve will be like Figure 3.8-7 on the oscilloscopescreen. It does not reflect the true shape of the hysteresis loop. It is necessary to adjustthe values of R2 and C appropriately to avoid this distortion
Figure 3.8-6. measuring arrangement with a digital oscilloscope The core under test is provided with two windings. The first winding (the number of turns N1) is fed with an alternating current 𝑖1 (the angular frequency 𝜔), it will cause a magnetomotive force F. Dependently of the distance traveled by the magnetic field lines, the magnetic circuit length L, it results in a magnetic field strength: 𝐻 = 𝑁1𝑖1 𝐿 Then the partial voltage on the resistor R1 is 𝑈𝑅1 = 𝑖1𝑅1 = 𝐿𝑅1 𝑁1 𝐻 The second winding is used for measuring the induction B. The generated electromotive force in this winding is proportional to the flux change 𝑑𝜓 within the core. Because the flux density is equal to the product of the magnetic induction and the cross sectional area of the core: 𝜓 = 𝐵𝑆, the relationship between the change of induction and electromotive force is: 𝑑𝐵 = 𝜀2𝑑𝑡 𝑁2𝑆 The current 𝑖2,can be calculated: 𝑖2 = 𝜀2 √𝑅2 2 + ( 1 𝜔𝐶 ⁄ ) 2 If 𝑅2 ≫ 1 𝜔𝐶 ⁄ , then the voltage on the capacitor C is 𝑈𝐶 = 𝑄 𝐶 = 1 𝐶 ∫ 𝑖2𝑑𝑡 = 𝑁2𝑆 𝐶𝑅2 𝐵 In the X-Y mode the field strength H (𝑈𝑅1 ) is plotted on the X-axis, and the flux density B (𝑈𝐶) on the Y-axis. Adjust the scope settings so that the hysteresis loop appears on the center of the axis and covers one full period. If 𝑅2 < 1 𝜔𝐶 ⁄ , then the 𝑈𝐶-𝑈𝑅1 curve will be like Figure 3.8-7 on the oscilloscope screen. It does not reflect the true shape of the hysteresis loop. It is necessary to adjust the values of R2 and C appropriately to avoid this distortion
UUFigure 3.8-7 distorted curvesExperimentalContentsandProcedures1. measure the magnetization curve and hysteresis loop of sample 1 under 50 HzAC signal.(1)Connect the cablesaccordingto thecircuit diagram showninFigure3.8-6.Thelines connected to the sample in the instrument are disconnected and need to beconnected with a wire.The solid line marked with a red arrow on the panel indicatesthe direction of the wiring, and the sample is replaced by changing the wiring position.Connect the voltage output end of Ri to the CHi channel of the oscilloscope, and thevoltage output end of Cto the CH2 channel of the oscilloscope.(2) Adjust the amplitude adjustment knob counterclockwise to minimize the excitationcurrent, and confirm that the values of Ri, R2 and C are not zero and meet theparameterrequirements.Note: The teacher will check the circuit before proceeding to the next step.(3) Switch on oscilloscope and apparatus of measuring magnetic hysteresis loop.Adjust the frequency to about 50 Hz. Press the MENU button in the horizontal controlarea of the oscilloscope to change the time base to X-Y mode; Press the POSITIONknob of CH1 and CH2 channels in the vertical control area to make the waveformdisplay in the center, then the coordinate is (o,O) grid on the center point of theoscilloscope; Set the coupling mode of CH1 and CH2 channels to DC (press theMENU button in trigger control area and select trigger setting to select the couplingmode).(4)clncrease the excitation current monotonically, that is, adjust the amplitudeadjustment knob clockwise slowly, so that the hysteresis loop displayed by the
Figure 3.8-7 distorted curves Experimental Contents and Procedures 1. measure the magnetization curve and hysteresis loop of sample 1 under 50 Hz AC signal. (1) Connect the cables according to the circuit diagram shown in Figure 3.8-6. The lines connected to the sample in the instrument are disconnected and need to be connected with a wire. The solid line marked with a red arrow on the panel indicates the direction of the wiring, and the sample is replaced by changing the wiring position. Connect the voltage output end of R1 to the CH1 channel of the oscilloscope, and the voltage output end of C to the CH2 channel of the oscilloscope. (2) Adjust the amplitude adjustment knob counterclockwise to minimize the excitation current, and confirm that the values of R1, R2 and C are not zero and meet the parameter requirements. Note: The teacher will check the circuit before proceeding to the next step. (3) Switch on oscilloscope and apparatus of measuring magnetic hysteresis loop. Adjust the frequency to about 50 Hz. Press the MENU button in the horizontal control area of the oscilloscope to change the time base to X-Y mode; Press the POSITION knob of CH1 and CH2 channels in the vertical control area to make the waveform display in the center, then the coordinate is (0,0) grid on the center point of the oscilloscope; Set the coupling mode of CH1 and CH2 channels to DC (press the MENU button in trigger control area and select trigger setting to select the coupling mode). (4)cIncrease the excitation current monotonically, that is, adjust the amplitude adjustment knob clockwise slowly, so that the hysteresis loop displayed by the
oscilloscope reaches saturation. Rotate the SCALE knob of CH1 and CH2 channels inthe vertical control area of the oscilloscope to adjust the voltage value represented bya large grid (Sx and Sy) of the oscilloscope, and press the SCALE knob to switchbetween coarse and fine adjustment. Reasonable adjustment of parameters Sx and Sy.and finally make the oscilloscope display a typical saturation hysteresis loop, andmake its vertex coordinates to (4.00, 4.00) grid and (-4.00, -4.00) grid (We can alsoadjust Ri to change the value of Ux, adjust R2 and C to change the value of Uy, andadjust the parameters Sx and Sy to change the scale of the graph). If the phase of thewaveform is distorted, the values of R2 and C should be adjusted to eliminate thedistortion.Note: After that, keep Sr, Sy,Ri,Rz and Cvalues fixed and recorded.(5) Reduce the excitation current monotonically, that is, adjust the amplitudeadjustment knob counterclockwise slowly until the final waveform is displayed as apoint to complete the demagnetization.(6) Measure the basic magnetization curveIncrease the excitation current monotonically, so that the X coordinates of the positivevertex of the hysteresis loop are 0,0.40,0.80, 1.20, 1.60,2.00, 2.40, 3.00, and 4.00grid, and record the corresponding Y coordinates.(7) Measure the dynamic hysteresis loopWhen the oscilloscope shows the typical beautiful limit hysteresis loop pattern, and itsvertexcoordinatesare(4.00.4.00)gridand(-4.00,-4.00)grid,recordtheYcoordinates of the hysteresis loop when the X co0rdinates are -4.00, -3.00, -2.00, -1.50,-1.00,-0.50,0.00,0.50,1.00,1.50,2.00,3.00,and 4.00respectively.2. measure the magnetization curve and hysteresis loop of sample 2 under 50 HzAC signal, and compare it with sample 1.The measurement method is the same as sample 1.Reference:https://collegedunia.com/exams/ferromagnetic-materials-chemistry-articleid-1995https://byjus.com/jee/ferromagnetic-materials/#：:text=Ferromagnetic%20Materials%20Ferromagnetic%20materials%20are%20a%2Ocertain%20group.to%20the%20alignment%20patterns%20of%20their%20constituent%20atoms.https://www.electronics-tutorials.ws/electromagnetism/magnetic-hysteresis.htmlhttps://meettechniek.info/passive/magnetic-hysteresis.html
oscilloscope reaches saturation. Rotate the SCALE knob of CH1 and CH2 channels in the vertical control area of the oscilloscope to adjust the voltage value represented by a large grid (Sx and Sy) of the oscilloscope, and press the SCALE knob to switch between coarse and fine adjustment. Reasonable adjustment of parameters Sx and Sy, and finally make the oscilloscope display a typical saturation hysteresis loop, and make its vertex coordinates to (4.00, 4.00) grid and (-4.00, -4.00) grid (We can also adjust R1 to change the value of Ux, adjust R2 and C to change the value of Uy, and adjust the parameters Sx and Sy to change the scale of the graph). If the phase of the waveform is distorted, the values of R2 and C should be adjusted to eliminate the distortion. Note: After that, keep Sx, Sy, R1, R2 and C values fixed and recorded. (5) Reduce the excitation current monotonically, that is, adjust the amplitude adjustment knob counterclockwise slowly until the final waveform is displayed as a point to complete the demagnetization. (6) Measure the basic magnetization curve Increase the excitation current monotonically, so that the X coordinates of the positive vertex of the hysteresis loop are 0, 0.40, 0.80, 1.20, 1.60, 2.00, 2.40, 3.00, and 4.00 grid, and record the corresponding Y coordinates. (7) Measure the dynamic hysteresis loop When the oscilloscope shows the typical beautiful limit hysteresis loop pattern, and its vertex coordinates are (4.00, 4.00) grid and (-4.00, -4.00) grid, record the Y coordinates of the hysteresis loop when the X coordinates are -4.00, -3.00, -2.00, - 1.50, -1.00, -0.50, 0.00, 0.50, 1.00, 1.50, 2.00, 3.00, and 4.00 respectively. 2. measure the magnetization curve and hysteresis loop of sample 2 under 50 Hz AC signal, and compare it with sample 1. The measurement method is the same as sample 1. Reference: https://collegedunia.com/exams/ferromagnetic-materials-chemistry-articleid-1995 https://byjus.com/jee/ferromagneticmaterials/#:~:text=Ferromagnetic%20Materials%20Ferromagnetic%20materials%20are%20a%2 0certain%20group,to%20the%20alignment%20patterns%20of%20their%20constituent%20atoms. https://www.electronics-tutorials.ws/electromagnetism/magnetic-hysteresis.html https://meettechniek.info/passive/magnetic-hysteresis.html