GENERAL PHYSICS LAB REPORT
Study of Ferromagnetic Materials
Date of submission - 25.09.19
Experiment date - 11.09.19 and 18.09.19
Submitted by:
PULKIT OJHA
1811118
2nd year, INT. MSc, SPS
Abstract
In this experiment, we were assigned the task of measuring the mag-
netic field in the given sample of ferro magnetic material at differ-
ent values of magnetic induction applied, and thus plot the magnetic
hysteresis loop for the material. We also had to try the process of
degaussing the material after noting the readings of hysteresis loop.
The value of magnetic field in the material was measured using the
gauss meter with the help of a Hall probe and to generate the required
magnetic induction, we used the coils as electromagnets.
Theory -
First of all, let’s discuss about the type of magnetism found in the ma-
terials and how do they react on the application of external magnetising
field. For which let’s define some vectors associated to the magnetism in
matter which are H and B where H is the applied magnetic field intensity
and B is the magnetic induction to be measured. Now, they’re related as
B = µ0 H
where µ0 is the permeability of vacuum. Inside a matter, there is Magne-
tization vector M which also effects the B to be measured. magnetization
vector denotes the dipolar magnetic moment of the material per unit vol-
ume.
B = µ0 (H + M )
1
Now, the relation between H and M is defined by a parameter known as
susceptibility of the material denoted by χ
M
χ= H
and with the help of different values χ can take, we’ll define the type of
magnetism found in materials.
1. Diamagnetism: Those solid matter which doesn’t have a permanent
magnetic moments in it’s atoms have this effect which is generally
very weak and is suppressed when para or ferromagnetism comes into
into picture. In these materials, M is in opposite direction of H and
thus χ < 0 .
2. Paramagnetism: In those solids which have permanent magnetic mo-
ments in their atoms, show the effect of paramagnetism, which pro-
duces a net non-zero M whenever some H is applied, in the same
direction as H. In this case, M varies linearly with H initially and
then reaches to a saturation level, but unlike the ferromagnetic ma-
terials , once the external field is removed, the magnetic moments
are disoriented and thus the χ value is positive but small for these
kind of materials.
3. Ferromagnetism: Now, there are some materials in which the value
of magnetisation is non-zero also without any external magnetiza-
tion. In these materials, there are regions where magnetic moments
have alligned them to get a net value called as magnetism domains,
therefore the χ value is positive and large. It’s a temperature depen-
dent phenomenon which exists below temperatures known as Curie’s
temperature.
For these materials, we can plot a curve between observed value of B and
applied value of H, that creates a loop known as Hysteresis loop.
In the above figure, the terms like coercivity and retentivity are the
properties of the ferro magnetic material and can be described as
1. Coercivity - The ability of the material to provide a resistance to
being demagnetised is known as coercivity.
2. Retentivity - The remanence of magnetization in the material when
no external magnetic induction is applied is known as retentivity.
2
Figure 1: Hysteresis loop
Apparatus: -
1. Iron Core
2. Pair of coils(600 turns each)
3. DC power supply
4. Digital Gauss Meter
5. Reversible Switch
6. Connecting Wires
3
OBSERVATION: -
SI NO. I(Amp) B(Gauss) H(A/m)
1 0.1 129 1392
2 0.21 305 662.8571429
3 0.3 537 464
4 0.4 752 348
5 0.5 982 278.4
6 0.6 1318 232
7 0.7 1439 198.8571429
8 0.8 1604 174
9 0.9 1797 154.6666667
10 1 1950 139.2
11 1.1 2080 126.5454545
12 1.2 2230 116
13 1.3 2370 107.0769231
14 1.4 2510 99.42857143
15 1.5 2630 92.8
16 1.6 2770 87
17 1.7 2890 81.88235294
18 1.8 3000 77.33333333
19 1.9 3130 73.26315789
20 2 3220 69.6
21 1.9 3180 73.26315789
22 1.8 3120 77.33333333
23 1.7 3040 81.88235294
24 1.6 2960 87
25 1.5 2870 92.8
26 1.4 2780 99.42857143
27 1.3 2670 107.0769231
28 1.2 2560 116
29 1.1 2440 126.5454545
30 1 2300 139.2
31 0.9 2170 154.6666667
32 0.8 2020 174
33 0.7 1850 198.8571429
34 0.6 1712 232
35 0.5 1512 278.4
36 0.4 1285 348
37 0.3 1042 464
38 0.2 797 696
39 0.1 502 1392
40 0 263 263
41 -0.2 -275 -696
42 -0.3 -292 -464
43 -0.4 -584 -348
44 -0.5 -856 -278.4
45 -0.6 -1153 -232
46 -0.7 -1370 -198.8571429
4
SI NO. I(Amp) B(Gauss) H(A/m)
47 -0.8 -1600 -174
48 -0.9 -1810 -154.6666667
49 -1 -2030 -139.2
50 -1.1 -2240 -126.5454545
51 -1.2 -2470 -116
52 -1.3 -2600 -107.0769231
53 -1.4 -2770 -99.42857143
54 -1.5 -2920 -92.8
55 -1.6 -3050 -87
56 -1.7 -3190 -81.88235294
57 -1.8 -3320 -77.33333333
58 -1.9 -3440 -73.26315789
59 -2 -3550 -69.6
60 -1.9 -3670 -73.26315789
61 -1.8 -3530 -77.33333333
62 -1.7 -3460 -81.88235294
63 -1.6 -3380 -87
64 -1.5 -3290 -92.8
65 -1.4 -3200 -99.42857143
66 -1.3 -3100 -107.0769231
67 -1.2 -2990 -116
68 -1.1 -2860 -126.5454545
69 -1 -2750 -139.2
70 -0.9 -2590 -154.6666667
71 -0.8 -2400 -174
72 -0.7 -2240 -198.8571429
73 -0.6 -2100 -232
74 -0.5 -1920 -278.4
75 -0.4 -1700 -348
76 -0.3 -1470 -464
77 -0.2 -1120 -696
78 -0.1 -937 -1392
79 0 -677 -677
80 0.1 -339 1392
81 0.2 -96 696
82 0.3 231 464
83 0.4 460 348
84 0.5 738 278.4
85 0.6 982 232
86 0.7 1238 198.8571429
87 0.8 1468 174
88 0.9 1688 154.6666667
89 1 1860 139.2
90 1.1 2050 126.5454545
91 1.2 2190 116
92 1.3 2360 107.0769231
93 1.4 2410 99.42857143
94 1.5 2650 92.8
95 1.6 2800 87
5
SI NO. I(Amp) B(Gauss) H(A/m)
96 1.7 2910 81.88235294
97 1.8 3030 77.33333333
98 1.9 3140 73.26315789
99 2 3250 69.6
Table 1: Magnetic field on Different Current
SI NO. I(Amp) B(Gauss) Bτ (Guass)
1 2 3250 240
2 -1.8 -3170 -650
3 1.6 2810 130
4 -1.4 -2970 -600
5 1.2 2450 120
6 -1.00 -2330 -600
7 0.80 1500 140
8 -0.60 -1530 -510
9 0.40 750 60
10 -0.20 -1070 -192
Table 2: Magnetic field on Different Current
Figure 2: Hysteresis Loop
6
CONCLUSIONS: -
1. The retentivity of the given sample is 263 Gauss.
2. The coercivity of the given sample is 213 Gauss.
3. The demagnetising table show how the material is demagnetised us-
ing magnetic fields in opposite directions alternatively.
Figure 3: Demagnetization of the sample
Reference: -
1. www.britannica.com/physics/hysteresis
2. https://www.ndt.net/events/APCNDT2017/app/content/Paper
