1. The document describes an experiment to measure and plot the B-H curve and permeability curve of a given material using a data logger, power supply, coils, cores and sensors. 2. A transformer is used to generate a magnetic field by passing a current through the primary coil, and the induced voltage in the secondary coil is measured to calculate the magnetic flux density B. 3. For a ferromagnetic material, B varies non-linearly with the magnetic field H, forming a hysteresis loop on the B-H curve whose area indicates energy loss per cycle.

2. AIM: 1. To study the B-H curve of the given material.
2. To study the permeability curve of the given material
APPARATUS: Data logger, power supply, two coil (300 turns),
U core, I core, voltage sensor (1V), current sensor (1A), resistor
module(5E,5W).
DESCRIPTION OF THE APPARATUS:
 The schematic diagram for the B-H curve setup is shown in Figure 1.
 Data logger is connected to the power supply. The data logger mainly
consists of 3 parts and are analog input, analog output and current
booster.
 A transformer is consisted of two coil (300turns) mounted on U core.
Left side of the coil is called as primary coil and that of the right side
coil is called as secondary coil.
 I core is placed on U core.
 All the connections are made according to the Figure 1.
 Now check Software of Deep Lite B-H curve on your computer.

3. Figure 1:The schematic diagram for the BH CURVE setup
FORMULA:
The magnetic induction, B is related to the magnetic field by the
following relation
𝐵 = 𝜇 𝑟 × 𝜇0 × 𝐻.
Where μ0 = vacuum permeability = 4π×10-7
volt. second/amp.
Meter
μr = relative permeability
In a transformer, when the current 𝐼1 in the primary coil of the
transformer increases (or decreases) linearly over time, it generates
magnetic field of strength:

4. 𝐻 =
𝑁1
𝐿
𝐼1 𝐴𝑚𝑝/𝑚𝑒𝑡𝑒𝑟.
Where L= Effective length of iron core,
𝑁1= Number of windings of primary coil.
𝐼1= Current in primary coil.
The corresponding magnetic induction value B can be obtained by
integration of the voltage 𝑉2 induced in the secondary coil of the
transformer:
𝐵 =
∫ 𝑉2 𝑑𝑡
𝑁2 𝐴
volt-second/meter2
Where
A= cross-section area of iron core.
𝑁2 = 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑤𝑖𝑛𝑑𝑖𝑛𝑔𝑠 𝑜𝑓 𝑠𝑒𝑐𝑜𝑛𝑑𝑎𝑟𝑦 𝑐𝑜𝑖𝑙.
𝑉2 = 𝐼𝑛𝑑𝑢𝑐𝑒𝑑 𝑣𝑜𝑙𝑡𝑎𝑔𝑒 𝑜𝑓 𝑠𝑒𝑐𝑜𝑛𝑑𝑎𝑟𝑦 𝑐𝑜𝑖𝑙.
Thus by exciting the primary coil with sinusoidal or triangular wave
of low frequency and then measuring the current (𝐼1) and induced
voltage(𝑉2), one can plot the B-H curve from measurements. One can
also obtain the values of 𝐵𝑟(remanence),𝐻𝑐(coercive force),
𝜇𝐼(initial permeability),𝜇 𝑎(max)(maximum amplitude permeability)
and area of closed loop under BH curve (hysteresis loss).

5. THEORY:
 Magnetic induction, (B):
 The total flux of magnetic field lines through a unit cross
sectional area of the material.
 Magnetic induction = B = Magnetic flux/Area = φ/A
 Magnetic field, (H):
 It is the portion of the space in which a magnetic body or a
current-carrying body can experience the magnetic force.
 The strength or the intensity of magnetic field is denoted by H
 Unit: Ampere/meter (A/m)
 Magnetic field is produced by permanent magnets such as horse
shoe magnet and temporarily by electromagnets or
superconducting magnets.
 Absolute Permeability, (μ):
 It is defined as the ratio of the magnetic induction B in the
medium to the magnetizing field H.
 Thus 𝜇 =
𝐵
𝐻
.
 Unit: henry/meter (H/m)

6.  Relative Permeability, (μr):
 It is defined as the ratio of the absolute permeability of the
material to the permeability of free space.μr =
𝜇
𝜇0
.
 μr is only a number and has no units
 For air or vacuum, μr = 1
B-H curve for a ferromagnetic material
 For a ferromagnetic material, magnetic induction, (B) varies
with the field (H) along a closed loop called the hysteresis loop.
Figure 2: BH curve for a ferromagnetic material.

7.  The curve begins at O. With increasing the values of
magnetizing field H, themagnetic flux density begins to increase
slowly. At sufficient high fields, it reaches a saturation value, Bs
and becoming independent of H. It is shown as OA in the figure.
 If H is decreased, B also decreases but following a path AC
instead of AO. Thus B legs behind H. When H becomes zero, B
does not become zero but has a value equal to OC and known as
remanent magnetism or residual magnetism, Br.
 It indicates that the material remain magnetized even in the
absence of the field H. The power of retaining the magnetism in
the absence of the field is called retentivity or remanence of the
material.
 Further if we increase the magnetic field in the reverse
directions, the value of B decreases along the path CD. It
becomes zero when H attains a value equal to OD (-Hc).
 The magnetic field Hc is referred as cohesive field. The
coercivity of the specimen is a measure of the magnetic field
required to destroy the residual magnetism in the material.
 If we increase magnetic field H further in reverse direction, the
value of B reaches a saturation value at a points E.

8.  On reversing the variation of the magnetic field, a curve similar
to ACDE is traced through point EFGA yielding a negative
remanence and coercivity.
 The closed curve ACDEFGA represents a cycle of
magnetization of the specimen and is known as hysteresis loop
of the specimen.
 The area of loop indicates the amount of magnetic energy loss
per unit volume of the material per magnetization
demagnetization cycle.
One can also plot the change in permeability 𝜇 𝑟 =
𝐵
𝜇0 𝐻
at different field
strength, H and the typical plot is shown in Figure 3.
Figure 3:the between field strength vs permeability.

9. PROCEDURE:
1. Make all the connection as shown in Figure 1 before you start the
experiment.
2. Keep the I core on U core.
3. Switch on the computer.
4. Click on the deep lite B-H curve software in the computer. Check the
display NO OF POINTS like Amplitude, samples, wave type.
5. Don’t change the wave type, core area, coil turns, core length and
time delay. Click on ok. Then you have the block diagram for B-H
curve.
7. Click on experiment and click on start experiment. Click on the
option B-H curve which was right side on the screen. Then you have the
B-H curve. From the curve, you can obtain the remenence, coercivity
and the enclosed area under BH loop.
8. Now click on the permeability. Then you have μr vs. H graph.
9. To save the graphs, open file and check the option to save graphs
and explore table data to csv.
10. Save the graphs and table data on the desktop with your name.

10. TABLE:
SAMPLE
Time
(Second)
Output
Voltage
Voltage
(Volt)
Current
(A)
H
( A/m
)
B
(V-
Sec/m²)
μ
( H/m) 𝜇 𝑟
1
2
3
4
5
6
.
.
.
.
.
.
.
.
.
.
.
201
GRAPHS:
Graph 1: B-H curve

11. Graph 2: μr-H curve
PRECAUTIONS:
1. Don’t remove the connections.
2. After taking data remove the I core from the U-core after
switching off the power supply.
3. Don’t remove the cable which was connected from the data
logger to monitor.
RESULT:
1. The variation of B vs. H is shown in Graph 1
2. The variation of relative permeability with field is shown in
Graph 2

12. VIVA QUESTIONS:
1. What do you meant by magnetic induction and magnetic
field?
2. How magnetic field and magnetic induction are related?
3. What is absolute permeability and how it is related to relative
permeability?
5.Which kind of material exhibit linear B-H curve?
6. What is residual magnetism?
7. What is cohesive field?
8. What is the physical significance of the area under BH curve?
9. What are the shapes of BH curve for different types of
magnetic material?
10. What are soft and hard magnetic material?