Physics Laboratory Manuals
for
B. Tech. II-Semester (Physics-II)
(As per the M D U University Syllabus)
Department of Applied Sciences
BRCM College of Engineering and Technology
Bahal - 127028, Dist. - Bhiwani, Haryana, India
Tel: +91 1255 265101-04
Fax: +91 1255 265217, 265110
Email: infocollege@brcm.edu.in
List of Experiments
PHY-203F : PHYSICS-II LAB
L T P Class Work 25 Marks
0 0 2 Exam 25 Marks
Total 50 Marks
Duration of Exam 3 Hrs.
Notes : The experiments in 1st semester will be based mainly upon Electricity, Magnetism, Modern
Physics and Solid State Physics which are the parts of theory syllabus.
1. To find the value of high resistance by Leakage method
2. To study the characteristics of a solar cell and to find the fill factor.
3. To find the ionization potential of Argon/Mercury using a thyratron tube.
4. To study the variation of magnetic field with distance and to find the radius of coil .
5. To study the characteristics of (Cu-Fe, Cu-Constantan) thermo couple.
6. To find the value of Planck's constant by using a photo electric cell.
7. To find the value of Hall Co-efficient of semi-conductor.
8. To study the V-I characteristics of a p-n diode.
9. To find the band gap of intrinsic semi-conductor using four probe method.
10. To calculate the hysteresis loss by tracing a B-H curve.
======================================================================
HIGH RESISTANCE BY LEAKAGE METHOD
OBJECT:
To determine the high resistance by the method of leakage of a condenser.
APPARATUS REQUIRED:
Ballistic Galvanometer, accumulator, Morse key, two way key
standard Condenser (capacity of the order of 1.0 or 0.5 µ.F), given resistor, stop watch and
connection wires.
FORMULA USED:
The high resistance R is given by
R = t / 2.3026 C log10 (θ0/θ1)
where,
t = time period of the leakage of condenser through the resistance,
θ0 = first throw of spot of light when initially the condenser is discharged through ballistic
galvanometer.
θ1 = first throw of spot of light when the condenser is discharged through the ballistic
galvanometer after a leakage of charge for time t through R.
C = capacity of the standard condenser.
HIGH RESISTANCE BY LEAKAGE METHOD
CIRCUIT DIGRAM:
PROCEDURE:
1. Make the electrical connections as in the circuit diagram.
2. Close K1 (ii) and press the Morse key (K2), i.e. charge the condenser for 40 seconds (say).
3. Release the Morse key K2 so that the condenser is discharged through the galvanometer.
Note down the first throw θ0.
4. Repeat the procedure of the points (ii) and (iii) several times, i.e. every time charge
condenser and then discharge through B.G. Obtain mean value of θ 0.
5. Closing K1 (ii) and pressing Morse key K2, charge the condenser for the same time.
Keeping Morse key pressed, open K1 (ii) and close K1 (i). Start the stop watch.
6. After a measured time t seconds (say 5 or 10 sec.), release Morse key and note down the
first throw θt in the galvanometer.
7. Repeat procedure (5) and (6) for different values of t.
HIGH RESISTANCE BY LEAKAGE METHOD
OBSERVATION TABLE:
Capacity of condenser = ……………. μF = …………… x 10-6 F
S.No.
Throw in the
galvanometer
θ0
Mean θ0
Leakage
time
T (in sec.)
Throw in
B.G.
θt
θ0/ θt
1.
2.
3.
4.
5.
GRAPH:
A graph is plotted with log10 (θ0/ θt) on Y-axis and‘t’ on X-axis as shown below:
HIGH RESISTANCE BY LEAKAGE METHOD
log10(θ0/ θt)
CALCULATIONS:
From the graph, obtain the slope which gives the value of log10(θ0/ θt)/t as shown in graph.
The resistance of the given resistor can be calculated as
R = t / 2.3026 C log10 (θ0/θ1) =
R = ………………Ohms
RESULT
:
Resistance of the given resistor is ………………….ohms.
PRECAUTIONS:
1. The galvanometer coil should be made properly free.
2. Connection should be proper & tight.
3. Tapping key should be used across the galvanometer.
4. Condenser should be free from dielectric loss.
5. After observing θ0, the galvanometer coil should be at rest for observing the value of θ t.
6. Switch ‘OFF’ the supply after completion of experiment.
HIGH RESISTANCE BY LEAKAGE METHOD
An experiment to measure the I-V characteristics of a
silicon solar cell
OBJECT:
To determine I-V characteristics of a silicon solar cell
APPARATUS REQUIRED:
Sample Silicon crystal solar cell, mill voltmeter (range from
100mV to 3V, electronic is better), Ammeter, Light Lamp.
THEORY:
Incident sunlight can be converted into electricity by photovoltaic conversion using a solar
panel. A solar panel consists of individual cells that are large-area semiconductor diodes,
constructed so that light can penetrate into the region of the p-n junction. The junction formed
between the n-type silicon wafer and the p-type surface layer governs the diode characteristics as
well as the photovoltaic effect. Light is absorbed in the silicon, generating both excess holes and
electrons. These excess charges can flow through an external circuit to produce power.
The following experiment was performed using a commercial polycrystalline silicon solar cell
with an active area of 5 cm X 1 cm. Under illumination from an artificial light source with an
intensity of 8.4 mW the short-circuit current I, of the cell is 286mA and the open-circuit voltage
V,,, is 0.466V. The basic equipment needed for this experiment is an ammeter, a voltmeter and a
decade box of resistors (0-100 kQ).
CIRCUIT DIGRAM:
I-V Characteristic curve of solar cell
PROCEDURE:
1. Make the electrical connections as shown in the circuit diagram.
2. Switch on the light lamp and keep it near to solar cell , light should fall on solar cell.
3. Take the observations by voltmeter (V) and Ammeter (I).
4. Plot the graph between V and I.
5. Change the distance between light lamp and Solar cell and repeat the step 3 and 4.
OBSERVATIONS:
Table of solar cell current and corresponding voltage:
Power
S.No.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
V (Volts)
I (m A)
I-V Characteristic curve of solar cell
GRAPH:
Graph between solar cell current and corresponding voltage
RESULT:
Characteristic curve of solar cell current and corresponding voltage for different distance is
attached.
---------------------------------------------
I-V Characteristic curve of solar cell
IONISATION POTENTIAL
OBJECT:
To determine the ionization potential of the gas filled thyratron.
APPARATUS REQUIRED:
A thyratron tube 884, two grid supplies (0-30 V), two voltmeters
(0-30 V), a micro-ammeter (or a sensitive galvanometer), two rheostats.
CIRCUIT DIGRAM:
Figure 1
Figure 2
IONISATION POTENTIAL
PROCEDURE:
1. Make the electrical connections as shown in fig. 1.
2. Keep both the grid and the plate at zero potential. There will be some deflection in the
microammeter on heating the filament. To reduce it to zero, apply just necessary negative
potential to the plate (keeping grid at zero potential). Keep this plate voltage constant
throughout the experiment.
3. Now apply positive potential to the grid. Increase it gradually in small steps and note down
the corresponding deflections in the microammeter (or galvanometer). It will be observed
that for a particular value of grid voltage, deflection increases very much.
4. Draw a graph between deflection (on Y-axis) and grid potential (X-axis) as shown in fig.3.
5. From the curve, the value of grid voltage corresponding to steep rise of microammeter
deflection (showing plate current) is calculated. This gives ionization plate potential (A)
of the gas filled in thyratron.
Correction factor due to initial velocity of the electrons:
6. Remove the microammeter from the plate circuit and connect it in the grid circuit as shown
in fig. 2
7. Keeping the same plate potential (fixed in point 2), give negative potential to the grid just
to reduce any deflection in microammeter to zero. Note down this value of ionization
potential. This is velocity correction ionization potential (B).
IONISATION POTENTIAL
OBSERVATIONS:
(A) Table for ionization plate potential:
S.No.
1.
2.
3.
4.
5.
6.
7.
Grid Potential
(in Volts)
Microammeter reading deflection
(µA)
Out of Scale
(B) Velocity correction ionization potential = ……………. Volts.
GRAPH:
Figure 3
IONISATION POTENTIAL
CALCULATIONS:
1. From the graph, we determine the value of ionization plate potential (A) as discussed in the
step 5 of the procedure.
2. The value correction-ionisation potential (B) is determined as discussed in steps 6 and 7 of
the procedure.
3. Correct Value of ionisation potential = A – B
RESULT:
Ionisation Potential of the gas is ……………Volts.
STANDARD RESULT:
………………Volts.
–
PERCENTAGE ERROR:
Therefore, Percentage Error = ………………….
PRECAUTIONS:
1. Microammeter or galvanometer used in the experiment should be very much sensitive.
2. Graph must be plotted carefully.
3. Velocity correction should be determined carefully.
---------------------------------------------
IONISATION POTENTIAL
Study the variation of the Variation of Magnetic
Field
OBJECT:
To plot graph showing the variation of magnetic field with distance along the axis of
a circular coil carrying current.
APPARATUS REQUIRED:
Tangent galvanometer of the Stewart and Gee type, a strong battery, a rheostat, a
commutator, plug key and connective wires.
FORMULA USED:
The field F along the axis of a coil is given by
Where n = number of turns in the coil
r = radius of the coils
i = current in ampere flowing in the coil
x = distance of the point from the centre of the coil.
If B is made perpendicular to H earth’s horizontal field, the deflection θ of the needle is given
by:
B = H tan θ
Variation of Magnetic Field
CIRCUIT DIGRAM:
PROCEDURE:
1. Place the magnetometer compass box on the sliding bench so that its magnetic needle is
at the centre of the coil. By rotating the whole apparatus in the horizontal plane, set the
coil in the agnetic meridian roughly.
2. In this case the coil, needle and its image all lies in the same vertical plane. Rotate the
compass box till the pointer ends read 0-0 on the circular scale.
3. To set the coil exactly in the magnetic meridian set up the electrical connections as in the
fig. Send the current in one direction with the help of commutator and note down the
deflection of the needle.
4. Now reverse the direction of the current and again note down the deflection. If the
deflections are equal then the coil is in magnetic meridian otherwise turn the apparatus a
little, adjust pointer ends to read 0-0 till these deflections become equal.
Variation of Magnetic Field
5. Using rheostat Rh adjust the current such that the deflections of nearly 70 o to 750 is
produced in the compass needle placed at the centre of the coil.
6. Read both the ends of the pointer. Reverse the direction of the current and again read
both the ends of the pointer. The mean of four readings will give the mean deflection at x
= 0.
7. Now shift the compass needle through 2cm. each time along the axis of the coil and for
each position note down the mean deflection. Continue this process till the compass box
reaches the end of the bench.
8. Repeat the measurements exactly in the same manner on the either side of the coil.
9. Plot a graph taking x along the axis and tan θ along the y-axis. Mark the points of
inflexion on the curve. The distance between the two points will be the radius of the coil.
OBSERVATIONS:
Distance (in cm)
S.No.
1.
2.
3.
4.
5.
6.
7.
Deflection
Out of Scale
RESULT:
The graph shows the variation of the magnetic field along the axis of a circular coil carrying
current.
PRECAUTIONS:
(i) The coil should be carefully adjusted in the magnetic meridian.
(ii) All the magnetic materials and current carrying conductors should be at a considerable
distances from the apparatus.
(iii) The current passed in the coil should be of such a value as to produce a deflection of nearly
750.
(iv) Current should be checked from time to time and for this purpose am ammeter should be
Variation of Magnetic Field
connected in series with the battery.
(v) Parallax should be removed while reading the position of the pointer. Both ends of the
pointer should be read.
---------------------------------------------
Variation of Magnetic Field
Study the variation of the thermo electric EMF
OBJECT:
To study the variation of the thermo electric e.m.f. with temperature, for a copperiron
APPARATUS REQUIRED:
Potentiometer( ETB type), standard cadmium cell, battery, a copper
Iron thermo-couple, high resistance box, high resistance rheostat, one way key, two way and
connection wires.
FORMULA USED:
The thermo electric e.m.f. (e) developed in a thermocouple is obtained with the
help of the following formula:
e = ρ El / R
Where ρ = resistance per unit length of the potentiometer wire,
E = resistance taken out from the resistance box (resistance across which the standard
cell is balanced)
L = length of the potentiometer wire when thermo e.m.f. is balanced.
CIRCUIT DIGRAM:
THERMOCOUPLE EXPERIMENT
PROCEDURE:
1. Make the electrical connections as shown in fig. 1.
2. Keep hot water pot on one end of couple.
3. Keep cold water pot on another end of couple.
4. Note the induced EFM by digital voltmeter with temperature of hot water.
5.
Repeat the process for decreasing temperature.
6. Draw a graph between EMF (on Y-axis) and temperature (X-axis) as shown in fig.2.
OBSERVATIONS:
(A) Room Temperature:
S.No.
1.
2.
3.
4.
5.
6.
7.
RESULT:
EMF
(in Volts)
Temperature of Hot Water
(µA)
Out of Scale
Characteristic of thermocouple is shown by the plotted graph
THERMOCOUPLE EXPERIMENT
PRECAUTIONS:
1. Dealing with hot water pot carefully.
2. Increments in temperature should slow.
3. Induced EMF takes some time for a stable reading.
---------------------------------------------
THERMOCOUPLE EXPERIMENT
Determining Planck's constant by photo cell
OBJECT:
To determine Planck's constant h and show that the kinetic energy of the electrons is
independent of the intensity of the light.
APPARATUS REQUIRED:
Vacuum type photo-emissive cell mounted in a wooden box provided
with a wide slit, optical bench with uprights, D.C. power supply, resistance box. Rheostat, a set f filters,
galvanometer, taping key, lamp and scale arrangements and connection wires.
FORMULA USED:
Electrons can be liberated from the surface of certain metals by
irradiating them with light of a sufficiently short wavelength (photoelectric effect). Their energy depends
on the frequency v of the incident light, but not on the intensity; the intensity only determines the number
of liberated electrons. This fact contradicts the principles of classical physics, and was first interpreted in
1905 by Albert Einstein. He postulated that light consists of a flux of particles, called photons, whose
energy E is proportional to the frequency f:
E
h⋅ f
We can determine Planck's constant h by exposing a photocell to monochromatic light, i.e. light
of a specific wavelength and measuring the kinetic energy E of the ejected electrons.
The value of Planck’s constant h is given by:
h = e (V2 – V1) λ1 λ2 / c(λ1 - λ2)
Where e = electronic charge ,V2 = stopping potential,V1 = stopping potential,c = velocity of light.
Planck's constant
CIRCUIT DIGRAM:
Fig 1 is a schematic representation of experiment
Fig-2 Setup for Planck Constant
PROCEDURE:
1. The electrical connections are made.
2. The lamp and scale arrangements are adjusted to get a well focused spot on the zero mark of the
scale. The photocell is mounted at one end of the optical bench. At the same level and nearly 3040 cm. from the photocell, a light source is arranged.
3. The light is allowed to fall on the cathode of photocell. Now a suitable filter of known
wavelength is placed in the path of ray reaching to photocell.
4. A random value is observed in Digital Ammeter .
Planck's constant
5. A small negative potential is applied on the anode by adjusting the rheostat Rh. This voltage is
recorded with the help of voltmeter. The corresponding Digital Ammeter.
6. The negative anode potential is gradually increased in small steps and each time corresponding
current is noted till the current is reduced to zero.
7. The experiment is repeated after replacing the green filter in succession by two filters e.g. blue
and yellow.
8. Taking negative anode potentials on X-axis and corresponding deflections on Y-axis, graphs are
plotted for different filters.
OBSERVATIONS:
Current and corresponding voltage for different filter:
Current
S.No.
Yellow filter
λ 1 = ….A0
Green Filter
λ 2 = ….A0
Blue filter
λ 3 = …..A0
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Planck's constant
Negative anode potential in
volts
GRAPH:
CALCULATIONS:
Electronic charge e = 1.6 x 10-19 coulombs
Speed of light c = 3 x 108 m/sec.
Wavelength of yellow filter λ1 = ………A0 = ….m
Wavelength of green filter λ2 = ………A0 = ….m
Wavelength of blue filter λ3 = ………A0 = ….m
1. for yellow and green filters
h = e (V2 – V1) λ1 λ2 / c (λ1 - λ2) = ………..joule-sec.
2. for green and blue filters:
h = e (V3 – V2) λ2 λ3 / c (λ2 - λ3) = ………..joule-sec.
3. for yellow and blue filters:
h = e (V3 – V1) λ1 λ3 / c (λ1 - λ3) = ………..joule-sec.
Mean value of Planck’s constant = ….+….+…./3 = ….joule-sec.
Standard Value: Standard value of Planck’s constant = 6.625 *10 joule-sec
Percentage Error:
% error = experimental value ~ standard value / standard value x 100 = …. %
Planck's constant
RESULT:
Observed value of Planck’s constant = ………………..joule-sec
STANDARD RESULT:
Standard value of Planck’s constant = 6.625 *10 joule-sec
–
PERCENTAGE ERROR:
Therefore, Percentage Error = ………………….
PRECAUTIONS:
1. The experiment should be performed in a dark room to avoid any stray light to photocell.
2. The observations should be taken by altering anode potential in small steps of 0.05volts
3. Corresponding to zero anode potential, the deflection of light spot on scale should be adjusted at
its maximum value.
4. Smooth graphs should be plotted.
5. Stopping potentials should be read carefully.
6. The experiment should be performed at least with three filters
---------------------------------------------
Planck's constant
Hall Effect Experiment
OBJECT:
To determine the Hall coefficient (RH ) of a semiconductor.
APPARATUS REQUIRED:
Hall Probe, Magnetometer, Electromagnet, Voltmeter Ammeter
.
FORMULA USED:
The Hall Effect is basic to solid-state physics and an important
diagnostic tool for the characterization of materials – particularly semi-conductors. It provides a
direct determination of both the sign of the charge carriers, e.g. electron or holes, and their
density in a given sample.
The Hall coefficient (RH ) of semiconductor is given by
RH=
--------------------------------------------(1)
where,(VH) is the Hall Voltages , t is thikness of specimen, I is Hall current and B z is applied
magnetic field
Charge Carriar Density
n=
--------------------------------------(2)
where e is electronic charge
Hall Effect Experiment
SETUP DIGRAM:
Figure 2
PROCEDURE:
Hall Effect Experiment
1. At room temperature and with a uniform magnetic field measure the Hall voltage as a
function of the current through the samples and plot the values on a graph.
2.
At room temperature and with a constant current through the sample, measure the voltage
across the sample (Sample voltage) as a function of the magnetic flux density, B, and plot the
results on a graph.
3. At room temperature, measure the Hall Voltage as a function of the magnetic flux density, B.
From the readings taken, determine the Hall coefficient, RH and the carrier density, n.
OBSERVATIONS:
(i)
Thickness of the crystal chop (W) = ………………..mm
(ii)
Hall Current (I) = ………………………………….mA
Table temperature and corresponding voltage:
S.No.
Magnetic Field Bz
in z Direction
in -z Direction
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Hall Effect Experiment
Hall Voltage
EXPRIMENTAL RESULT:
Hall Coefficient for Germanium is ……………..
STANDARD RESULT:
Hall Coefficient for Germanium is ………………
–
PERCENTAGE ERROR:
Therefore, Percentage Error = ………………….
PRECAUTIONS:
1. The resistivity of the Hall Probe should be uniform in the area of measurement.
2. The surface on which the probes rest should be flat with no surface leakage.
3. The gap of the electromagnet from probes should be small compared.
4. Avoid any other magnet keeping near to experiment setup
5. Do not ware wristwatch during experiment.
---------------------------------------------
Hall Effect Experiment
V-I CHARACTERISTICS OF A DIODE
OBJECT:
To study the V-I characteristics of a PN-junction diode.
APPARATUS REQUIRED:
Diode Characteristics Kit, Power Supply, Ammeter (0-20mA),
Voltmeter (0-20V), Connecting Leads.
A P-N junction is known as Semiconductor diode or Crystal diode. It is a
BRIEF THEORY:
combination of P-type & N-type Semiconductor which offers nearly zero
resistance to current on forward biasing & nearly infinite Resistance to the flow of current when
in reverse biased.
Forward biasing: When P-type semiconductor is connected to the +ve terminal and N-type
to –ve terminal of voltage source. Nearly zero resistance is offered to the flow of current in this
condition.
Reverse biasing: When P-type semiconductor is connected to the –ve terminal and N-type to +ve
Terminal. Nearly zero current flow in this condition.
CIRCUIT DIGRAM:
Figure 1 (Forward Biased)
Figure 2 (Reverse Biased)
V-I CHARACTERISTICS OF P-N JUNCTION DIODE
PROCEDURE:
1. Wire up the circuit shown in figure 1 for forward biased diode.
2. Record the voltage across the diode (V) and current (I) through it as a function of input
voltage.
3. Repeat the experiment for the reverse biased diode (fig 2).
4. Plot the relevant graphs.
OBSERVATION TABLE:
S.No.
1.
When diode is forward biased
Current(mA)
Voltage(V)
When diode is reverse biased
Current(μA)
2.
3.
4.
5.
GRAPH:
V-I CHARACTERISTICS OF P-N JUNCTION DIODE
Voltage(V)
RESULT:
The V-I characteristic of PN-junction diode is shown in form of graph.
PRECAUTIONS:
1. Always connect the voltmeter in parallel & ammeter in series as shown in circuit
diagrams.
2. Connection should be proper & tight.
3. Switch ‘ON’ the supply after completing the circuit.
4. DC supply should be increased slowly in steps starting from zero value.
5. Reading of voltmeter & Ammeter should be taken accurately.
6. Switch ‘OFF’ the supply after completion of experiment.
V-I CHARACTERISTICS OF P-N JUNCTION DIODE
SEMICONDUCTOR ENERGY BAND GAP
OBJECT:
To determine the energy band gap of a semiconductor (Germanium) using four probe
method.
APPARATUS REQUIRED:
Four probe arrangement (probes coated with Zinc at tips), sample
(Germanium crystal with non-conducting base), oven (for the variation of temperature of the
crystal from room temperature to about 2000C), a constant current generator (open circuit voltage
about 20 V, current range 0 to 10 mA), millivoltmeter (range from 100mV to 3V, electronic is
better), power supply for oven, thermometer.
FORMULA USED:
The energy band gap, Eg, of semiconductor is given by
--------------(1)
where,
k is Boltzmann constant equal to 8.6 X 10-5 eV/deg. &
ρ is the resistivity of the semiconductor crystal, given by
--------------(2)
where
(in Ω-cm)----------------(3) ;
SEMICONDUCTOR ENERGY BAND GAP
s is the distance between probes and W is the thickness of semiconducting crystal ;
V and I are the voltage and current across and through the crystal chip respectively.
For f (W/s), refer to the table given below:
W/s
f (W/s)
0.100
13.863
0.141
9.704
0.200
6.931
0.333
4.159
0.500
2.780
1.000
1.504
1.414
1.223
2.000
1.094
3.333
1.0228
5.000
1.0070
10.000
1.00045
Table 1
If any (W/s) value is not found in the table above, plot a graph between these (W/s) and f (W/s)
values and from the graph, the desired value of f (W/s) corresponding to any value of (W/s) can
be found out.
CIRCUIT DIGRAM:
SEMICONDUCTOR ENERGY BAND GAP
PROCEDURE:
1. Make the electrical connections as shown in the circuit diagram.
2. Switch on the constant current source and adjust current I, to a desired value, say 2 mA.
3. Place four probe arrangement in the oven. Fix the thermometer.
4. Connect the oven power supply and start heating.
5. Measure the inner probe voltage V, for various temperatures.
OBSERVATIONS:
(i)
Distance between probes (s) = …………… mm
(ii)
Thickness of the crystal chop (W) = ………………..mm
(iii)
Current (I) = 2 mA
Table temperature and corresponding voltage:
Temperature
S.No.
in 0C
in K
Voltage
(V)
(in Volts)
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
SEMICONDUCTOR ENERGY BAND GAP
GRAPH:
SEMICONDUCTOR ENERGY BAND GAP
CALCULATIONS:
1. First find the resistivity ρ, corresponding to temperatures in K using relation (2) where ρo is
given by relation (3). Corresponding to different values of V, there will be different values
of ρo.
2. Find W/s & then corresponding to this value choose the corresponding f(W/s) from table 1
or by the graph made as discussed in the formula used.
3. After getting f(W/s), calculate the value of resistivity, ρ, for various values of ρo, i.e., for
various values of V which correspond to the various values of temperature and tabulated as
follows:
S.No.
Temperature, T
Resistivity, ρ
(K)
(Ω-cm)
X103
log10ρ
4. Finally, plot a graph between log10ρ and x 103 and find the slope of the curve as shown in
graph.
5. Find the energy band gap of the given semiconductor sample using the formula
= 2k x 2.3026 x (AB/BC) x 1000
= 2 x 8.6 x 10-5 x 2.3026 (AB/BC) x 1000 eV
=0.396 x (AB/BC) eV
SEMICONDUCTOR ENERGY BAND GAP
RESULT:
Energy bandgap for Germanium is …………….. eV.
STANDARD RESULT:
………………eV.
–
PERCENTAGE ERROR:
Therefore, Percentage Error = ………………….
PRECAUTIONS:
1. The resistivity of the material should be uniform in the area of measurement.
2. The surface on which the probes rest should be flat with no surface leakage.
3. The diameter of the conduct between the metallic probes and the semiconductor crystal
chip should be small compared to the distance between the probes.
---------------------------------------------
SEMICONDUCTOR ENERGY BAND GAP
HYSTERESIS LOSS
OBJECT:
To determine hysteresis loss by C.R.O.
APPARATUS REQUIRED:
A step down transformer, specimen (internal built or external),
capacitor (8 μF), resistor (50 KΩ potentiometer), A.C. Voltmeter (0-10 V), A.C. milliammeter
(0-500 mA), rheostat (10 Ω)
FORMULA USED:
Hysteresis loss per unit volume per cycle is given by
W=
where,
i = current in the primary winding in amperes,
V = voltage across primary winding corresponding to i.
f = frequency of A.C. = 50 cycles/sec.
*Area can be counted in mm2 from the centimeter graph of B-H loop by counting the small
squares of mm.
HYSTERESIS LOSS
CIRCUIT DIGRAM:
PROCEDURE:
1. Apply some voltage , V, with the help of rheostat, Rh. Connect XX plates and YY plates of
C.R.O.
OBSERVATION TABLE:
Capacity of condenser = ……………. μF = …………… x 10-6 F
S.No.
Throw in the
galvanometer
θ0
Mean θ0
Leakage
time
T (in sec.)
1.
2.
3.
HYSTERESIS LOSS
Throw in
B.G.
θt
θ0/ θt
log10(θ0/ θt)
4.
5.
R = t / 2.3026 C log10 (θ0/θ1) =
GRAPH:
CALCULATIONS:
From the graph, obtain the slope which gives the value of log10(θ0/ θt)/t as shown in graph.
The resistance of the given resistor can be calculated as
HYSTERESIS LOSS
R = ………………Ohms
RESULT:
Resistance of the given resistor is ………………….ohms.
PRECAUTIONS:
1. The galvanometer coil should be made properly free.
2. Connection should be proper & tight.
3. Tapping key should be used across the galvanometer.
4. Condenser should be free from dielectric loss.
5. After observing θ0, the galvanometer coil should be at rest for observing the value of θ t.
6. Switch ‘OFF’ the supply after completion of experiment.
HYSTERESIS LOSS