Institute of Space Technology: Applied Physics Lab
Institute of Space Technology: Applied Physics Lab
Institute of Space Technology: Applied Physics Lab
Lab Report # 2
Submitted to:
Ma’am Khola Anees
Submitted by:
Group Members
Haider Ali
Wajahat Ali
The Server
Contents
LEANING OUTCOME:..............................................................................................................................3
OBJECTIVE:..............................................................................................................................................3
THEORETICAL BACKGROUND:............................................................................................................3
Electrical energy:.....................................................................................................................................3
Ferromagnetism:......................................................................................................................................4
Curie temperature:...................................................................................................................................4
Para magnetism:......................................................................................................................................4
Kanthal-D wire:.......................................................................................................................................5
Stefan-Boltzmann Law:...........................................................................................................................6
Apparatus:...................................................................................................................................................6
2) Control box:.....................................................................................................................................6
3) Stopwatch:.......................................................................................................................................7
4) Clamp meter:...................................................................................................................................7
5) Safety gloves:..................................................................................................................................7
7) Kanthal wire:...................................................................................................................................8
Methodology:..............................................................................................................................................8
Calculations:................................................................................................................................................9
Result:.......................................................................................................................................................11
Conclusion:................................................................................................................................................11
Sources of Error:.......................................................................................................................................11
Bibliography:.............................................................................................................................................12
QUESTION ANSWERS...........................................................................................................................13
1
Magnetic Phase Transition 2016
Figure 1(Magnetic Phase Transition)...........................................................................................................3
Figure 2(Ferromagnetism)...........................................................................................................................4
Figure 3(Para magnetism)...........................................................................................................................5
Figure 4(Kanthal-D Wire)...........................................................................................................................5
Figure 5(Variable Transformer)...................................................................................................................6
Figure 6(Control Box).................................................................................................................................7
Figure 7(Stopwatch)....................................................................................................................................7
Figure 8(Clamp meter)................................................................................................................................7
Figure 9(Safety gloves)...............................................................................................................................8
Figure 10 (Pole for wire & magnet assembly).............................................................................................8
Figure 11 (Kanthal-D Wire)........................................................................................................................8
Figure 12(Experimental Setup)....................................................................................................................9
Figure 13(Voltage, Current & Time Values).............................................................................................10
Figure 14(FUSE & BREAKER)................................................................................................................15
Figure 15(EARTH WIRE).........................................................................................................................15
Table 1(Curie temperature of materials)......................................................................................................4
Table 2(Heat capacities of Different Substances)........................................................................................5
Table 4(Curie equation constants).............................................................................................................10
Table 5(KANTHALD-WIRE Properties)..................................................................................................13
2
Magnetic Phase Transition 2016
LEARNING OUTCOME:
In this experiment, we will
1. Learn how to handle large currents safely.
2. Understand the concept of electrical properties of materials and magnetism of
different materials.
3. Familiarize ourselves with common electrical test equipment such as the voltmeter,
ammeter, Multimeter, clamp meter and circuit components such as the circuit breaker
and variable transformer (VARIAC).
4. Effect of voltage on material & its magnetic phase transitions.
OBJECTIVE:
To calculate the Curie temperature of a ferromagnetic material i.e. Kanthal-D
wire by varying the amount of voltage and current passing through it. Values of voltage,
current and the time at which wire get demagnetized needs to be measured and then an
appropriate set of calculations need to be carried out in order to calculate the Curie
temperature.
THEORETICAL BACKGROUND:
3
Magnetic Phase Transition 2016
Electrical energy:
Electrical energy is energy that is caused by moving electric charges. Since
the electric charges are moving, this is a form of kinetic energy. The faster
the electric charges are moving the more electrical energy they carry.
Ferromagnetism:
These are the materials that can be magnetized by an external magnetic field
and remain magnetized after the external field is removed. In the presence of magnetic field
the domain of ferromagnetic becomes aligned and they remain aligned for a long time even
after the magnetic field is removed.
Only a few substances are ferromagnetic. The common ones are iron, nickel, cobalt
and most of their alloys like alnico (aluminum nickel cobalt), some compounds of rare earth
metals, and a few naturally-occurring minerals such as lodestone.[ CITATION htt \l 1033 ]
Figure 2(Ferromagnetism)
Curie temperature:
It is the temperature at which certain magnetic materials undergo a sharp change in their
magnetic properties i.e. it changes from ferromagnetic to paramagnetic because on increasing
the temperature the domains of the ferromagnetic material no longer remain aligned. At
certain temperature (Curie temperature) the domains become so distorted that ferromagnetic
is converted to paramagnet. [ CITATION htt1 \l 1033 ]
Para magnetism:
These materials are slightly attracted by a magnetic field and the material does not
retain the magnetic properties when the external field is removed. Paramagnetic properties
are due to the presence of unpaired electrons, and from the realignment of the electron paths
caused by removing the external magnetic field.
4
Magnetic Phase Transition 2016
Paramagnetic materials include magnesium, molybdenum and lithium.
5
Magnetic Phase Transition 2016
Substance Specific heat capacity in J / kg °C
Water 4181
Oxygen 918
Lead 128
Apparatus:
1) Variable Transformer (VARIAC)
The VARIAC is a variable transformer with a range of 0V-250V. The AC
mains supply from WAPDA (or the local generator) is connected across the primary
coil and the variable output is taken from the sliding contact on the output side. The
voltage is step down in the ratio of
V out N out I out
= =
V¿ N¿ I¿
Where N ¿and N out are the total number of turns in the primary coil and the turns
between the output tap and ground.
2) Control box:
It is used to switch the circuit ON and OFF. It also has an emergency stop
button and a circuit breaker along with a built-in voltmeter and an ammeter.
6
Magnetic Phase Transition 2016
Figure 7(Stopwatch)
4) Clamp meter:
It measures the current passing through the wire. Currents are measured with the help
of a clamp meter. The jaws of the clamp meter surround the wire through which the
current is to be determined. Its range is 200A-600A.
5) Safety gloves:
To ensure safety from high voltages. It is made of insulator (i.e. Rubber)
7
Magnetic Phase Transition 2016
Methodology:
1) Set up the apparatus as shown.
8
Magnetic Phase Transition 2016
Calculations:
Measurement of Curie temperature:
The electrical energy supplied in a certain interval of time is defined as
ET = Power × time = P ×t
Power = Voltage × current = V × I
ET = VIt ……………………………………… (1)
9
Magnetic Phase Transition 2016
m = mass of the wire and
c = specific heat capacity.
Where
T C = Curie temperature,
ε = is the emissivity,
σ = 5.675 ×10−87W/m 2 K 4 (Stefan-Boltzmann constant)
S = surface area of the heating element ( πdL)
Substituting equations (1), (2) and (3) in the Energy equation we get
4
Tc = 4 VI + ԑσS T o ……………………… (4)
√ ԑσS
The constant values required for this calculation are given in the following table.
Emissivity of the wire (ϵ) 0.7
Boltzmann constant (σ ) 5.675×10-8 W/m 2 K 4
Length of Kanthal wire (L) 1m
Diameter of the Kanthal wire 4.5E-3m
Room temperature (TO) 26OC or 299 K
Put these values into the equation (4) to calculate the Curie temperature,
VI
TC
√
= 4 ԑσS +T 4o
( 22.33 V )( 6.21 A )
√
T C= 4 −8 2 4 2
( 0.7 ) ( 5.675 × 10 W /m K )( 0.014 m )
+(299 K) 4
10
Magnetic Phase Transition 2016
( 22.33 ) ( 6.21 ) W
√
T C= 4 −8 2 4 2
( 0.7 ) ( 5.675 × 10 W /m K )( 0.014 m )
+(299 K) 4
4
T C =√ 2.49∈ 11 K 4 +7.99 ∈10 K 4
4
T C =√ 3.289∈ 11 K 4
T C =757.29 K
Result:
The Kanthal D-wire used in the current experiment demagnetized at a curie temperature of
757.29 K(i.e. 484.29 OC).
Conclusion:
The value calculated from this experiment is therefore, exhibiting an error of 19.28%.
Moreover, it can also be observed that the time for which the Kanthal wire remains attached
to the magnet decreases as the amount of voltage passing through it increases so it can be
deduced that the Kanthal wire loses its magnetism more quickly as the rate of heat energy
provided to it increases as its domains lose their alignment more quickly.
Sources of Error:
1) The numbers of values taken from the experiment are not enough so more readings
should be taken and a graph should be plotted to obtain a more accurate value.
2) The uncertainties in the values of voltage, current, time and emissivity are not taken
into account so they should be considered when calculating the value of Curie
temperature.
3) The time calculated with the help of stopwatch is not accurate due to the addition of
human reaction time so a system of sensors connected to an electronic stopwatch
should be used.
Bibliography:
1. [Online] http://en.wikipedia.org/wiki/Ferromagnetism.
11
Magnetic Phase Transition 2016
2. [Online] http://www.britannica.com/EBchecked/topic/146902/Curie-point.
4. [Online] http://kanthal.com/en/products/material-datasheets/wire/resistance-heating-wire-
and-resistance-wire/kanthal-d/.
12
Magnetic Phase Transition 2016
QUESTION ANSWERS
Q1: What is coercivity?
Ans: For ferromagnetic material the coercivity is the intensity of the applied magnetic field
required to reduce the magnetization of that material to zero after the magnetization of the
sample has been reached to saturation.
Ans: We use AC due to its less power loss and its ability to be stepped down and step up
the voltage for different household appliances by using transformers, which DC cannot do. It
can also be transferred to long distances with less power loss.
Property Value
Ans: Scientists believe the magnetic field is generated deep inside the Earth where the
heat of the planet's solid inner core churns a liquid outer core of iron and nickel. The solid
inner core is thought to be a mass of iron about the size of the moon that is heated to several
thousand degrees Fahrenheit.
13
Magnetic Phase Transition 2016
Ans:
S.NO. HARD MAGNETIC SOFT MAGNETIC MATERIALS
MATERIALS
1 Materials which retain their Soft magnetic materials are easy to
magnetism and are difficult to magnetize and demagnetize.
demagnetize are called hard These materials are used for making
magnetic materials. temporary magnets. The domain wall
These materials retain their movement is easy. Hence they are easy to
magnetism even after the removal of magnetize. By annealing the cold worked
the applied magnetic field. Hence material, the dislocation density is reduced
these materials are used for making and the domain wall movement is made
permanent magnets. In permanent easier. Soft magnetic materials should not
magnets the movement of the possess any void and its structure should be
domain wall is prevented. They are homogeneous so that the materials are not
prepared by heating the magnetic affected by impurities.
materials to the required temperature
and then quenching them. Impurities
increase the strength of hard
magnetic materials.
2 They have large hysteresis loss due They have low hysteresis loss due to small
to large hysteresis loop area. hysteresis area.
3 Coercivity and retentivity values are Coercivity and retentivity values are less.
large.
4 Magnetic energy stored is high. Since they have low retentivity and
coercivity, they are not used for making
permanent magnets.
5 They possess high value of BH Magnetic energy stored is less.
product.
6 The eddy current loss is high. The eddy current loss is less because of
high resistivity.
Ans: steel is a better material to make permanent magnet as it’s coercivity as well its
hysteresis loop is greater which means it requires more energy to magnetize as well
demagnetize.
Q9: How does the clamp meter work will it work for DC?
Ans: Ordinary clamp meters used to measure AC currents work on the principle of
electromagnetic induction caused by the alternating current flowing in the conductor which
reverses direction causing a dynamically changing magnetic field. However, in DC
14
Magnetic Phase Transition 2016
conductors, the current flows in a fixed polarity. Consequently, the magnetic field around the
conductor is fixed and does not change. Hence, a conventional clamp meter will register no
reading. But a special modified one does.
Ans: The earth wire is a crucial part of the home electrical system and is designed to protect
against electric shock. If faults occur in the electrical system, the electricity will flow to
earth by the shortest and easiest path.
Ans: These are one of the Basic Switching Element in the High Power Electrical circuits, in
which through small current (or power), Higher Current (or power) can be controlled. From
15
Magnetic Phase Transition 2016
two Basic switching elements (i.e. like push button or on/off switch) Magnetic contactor
work in a place where the later one is required.
Ans:
Q14: Why have we used porcelain for mounting the heating element on the pole?
Ans: It is a very Good ceramic electrical insulator, it can bear greater degree of temperature
than other insulators with having little effect on its properties. Moreover it is capable of
holding the weight or tension of the material to be hanged.
Q15: Why can’t we attach magnets directly to the metallic poles, why do we need to insert
alumina ceramic in between?
Ans: Since magnets are used to magnetize Kanthal D-wire, therefore they are connected to
it through insulator. What might happen if this insulator fails is, current directly flows
through the magnets and through it to the pole, if another insulator (Alumina silicate) is not
used as precautionary. If there is no insulator between magnets and pole than not even
magnets would be destroyed because of high current but also it will make the system short, as
the pole is connected to the earth.
Ans: The tip of the tester is touched to the conductor being tested (for instance, it can be
used on a wire in a switch, or inserted into a hole of an electric socket). A neon lamp takes
very little current to light, and thus can use the user's body capacitance to earth ground to
complete the circuit.
Q: 17 what are the different color codes for wires in live, neutral and earth? Also suggest
why additional colors are used?
The electrical color coding system is used is active (live) brown (red); neutral, blue (black);
and earth, green/yellow strip (green).
These are the color codes for wires carrying D.C current, but to completely define the A.C
current one must use additional colors to describe the phase shift between the live wires.
Therefore two additional colors are being standardized for the purpose.
Q: 18 what is Exchange Energy?
Ans: Exchange Energy is that energy which is the amount of energy transferred by a high
energy domain to a lower energy domain so as to keep it aligned and keeping the overall
magnetic effect by keeping mutual alignment of the magnetic fields of the domains. That
energy transferred is called exchange energy.
Q: 19 what will happen when thermal energy overcomes the exchange energy?
16
Magnetic Phase Transition 2016
Ans: The thermal energy makes the atoms vibrate faster and lose their alignments at
temperatures where thermal energy overcomes the exchange energy which is called the curie
temperature, substances lose their magnetization due to the disturbed alignment of their
atoms which disturbs the overall field alignment and hence a Ferro magnet is converted into a
para magnet, this temperature varies for different substances.
Q: 20 identify any three paramagnetic materials in your surroundings?
Ans: there are many paramagnetic materials surrounding us, e.g. aluminum (used as foils
etc.), platinum (used in jewelry, and electro plating) and potassium, these substances have
dipoles randomly arranged so that there is no overall net magnetic field.
=================================END=============================
17