EXPERIMENT 1

AIM : Electric Field between Parallel Conductors

Requirement:
1. Conducting sheet
2. Conducting Strip
3. Multimeter
4. Power Supply
5. Probe

THEORY :

Mount the conductive paper with the two parallel conductors to the corkboard by
placing a plastic pushpin in each corner of the semi-conducting paper.
Please place the pushpins in existing holes to prevent damaging the paper and
putting unnecessary holes in the conductor.
Push an aluminum push pin into each of the two conducting electrodes (metallic
stripes) on the paper. These aluminum push pins are electrically conducting, and are
used to make connections to the electrodes.
Connect the (−) terminal of the power supply to one of the parallel conductors (the
one on your left)and the (+) terminal to the one on your right using the banana-
alligator clip leads.
A power supply is a source of voltage. It can be a battery, a cell phone charger, or a box
like the one you will use. It has at least two output jacks to which you attach conducting
wires. The knob on the power supply controls the difference in voltage, or electric
potential difference, between the two jacks. While one always measures a voltage
difference between two points, we often refer to one jack as “common” or zero voltage.
So when we say a power supply “puts out 5 V” what we mean is that there is a difference
of 5 V between the two output jacks.
The meter you will use can measure several things, and is called a “multimeter.”
You will become more familiar with it over the next few weeks. It can measure
voltage differences, currents, and resistance, Today, you will use it only as a
voltmeter to measure the voltage difference between two points that you touch the
voltmeter probes to.
 EXPERIMENT 2

AIM : Measurement of Electric Field Pattern Between Two Circular Electrodes

REQUIREMENT : Two electrodes, Manifold paper, Carbon paper, Only carbonate plate,
needle, Digital multimeter.

THEORY :With this experiment the students will investigate the electric field between two
circular electrodes. This field corresponds to the attractive field between two point charges. It is
also referred to as a static dipole field and serves as an example of an inhomogeneous field.
To be well prepared for the experiment, the students should be familiar with the concepts
of equipotential lines and field lines. They should know that a voltage is equivalent to the
difference in electric potentials between two points of an electric field, and that applying a
voltage to two electrodes causes an electric field to build up. What is more, they should
know that, according to the concept of field lines, the density of the field lines is
proportional to the electric field strength, or the strength of the electric force respectively.

DIAGRAM:
Use a pencil and connect the points of equal electric potential as
equipotential lines. Label each line by its electric potential.
Equipotential lines of the electric field are plotted on the carbon paper (Fig. 15).
EXPERIMENT 3

AIM :To determine the Standing Wave-Ratio and Reflection Coefficient

Apparatus required:
1 Klystron power supply
2 Klystron tube
3 SWR meter
4 Isolator
5 Frequency meter
6 Variable attenuator
7 Slotted line
 8 Tunable probe
9 Wave guide stand
10 Matched Termination
11 BNC cable
12 S-S tuner

Theory:
It is a ratio of maximum voltage to minimum voltage along a transmission line called SWR, as
ratio of maximum to minimum current. SWR is a measure of mismatch between load and line.
The electromagnetic field at any point of transmission line may be considered as the sum of two
traveling waves: the 'Incident Wave' propagates from generator and the reflected wave
propagates towards the generator. The reflected wave is set up by reflection of incident waves
from a discontinuity on the line or from the load impedance. The magnitude and phase of the
reflected wave depends upon amplitude and phase of the reflecting impedance. The
superposition of two traveling waves, gives rise to standing waves along with the line. The
maximum field strength is found where two waves are in phase and minimum where the line
adds in opposite phase. The distance between two successive minimum (and maximum) is half
the guide wavelength on the line. The ratio of electrical field strength of reflected and incident
waves is called reflection between maximum and minimum field strength along the line.

DIAGRAM:
 EXPERIMENT 4

AIM :Measurement of Dielectric constant.

REQUIREMENT :
1. Set of parallel plate capacitors (Diameter = 26 cm)
2. High voltage power supply (0-10kV)
3. A 10 MΩ resistor
4. Reference capacitor (220nF)
5. Universal measuring amplifier
6. Voltmeter
7. Dielectric materials (Plastic and glass plates)
8. Connecting cables, adapters, T-connectors

Theory:
Electrostatic processes in vacuum are described by the following integral form of
Maxwell’s equations:
∯𝑬. 𝒅𝑨 = Q (1)
s0

∮ 𝑬.𝒅𝑺 = 0 (2)
whereE is the electric field intensity, Q the charge enclosed by the closed surface A, 𝜀Ois the
permittivity of free space and s a closed path. If a voltage Uc is applied between two
capacitor plates, an electric field E (Fig. 1) will prevail between the plates, which is defined
by:
2
𝑈c= ∫1 𝑬. 𝒅𝒓 (3)

Due to the electric field, equal amount of electrostatic charges with opposite sign are
drawn towards the surfaces of the capacitor. Assuming the field lines of the electric field
always to be perpendicular to the capacitor surface, for small distances d between the
capacitor plates, Eq. 1 and 3 give
Q =Uc.Æ
s0 (4)
d

The charge Q on the capacitor is thus proportional to voltage the

proportionality constant C is called the capacitance of the plate capacitor.
𝑄 = 𝐶𝑈𝑐 = 𝜀0 𝑈 (5) 𝐴
𝑑 c

The linear relation between charge Q and voltage Uc applied to the

otherwise unchanged capacitor is represented in fig. 4. Eq. 5 further shows
that the capacitance C of the capacitor is inversely proportional to the
distance d between the plates and directly proportional to the area A of the
plates:
𝐶 = 𝜀0 𝑑 𝐴 (6)
Fig. 1: Electric field
lines between capacitor plates
Equations (4), (5) and (6) are valid only approximately, due to the assumption that field lines
are parallel. With increasing distances between the capacitor plates, capacitance increases,
which in turn systematically yields a too large electric constant from equation (6). This is
why the value of dielectric constant should be determined for a small and constant distance
between the plates (Fig. 1).
Once an insulating material (dielectrics) is inserted between the plates the above equations
are modified. Dielectrics have no free moving charge carriers, as metals have, but they do
have positive nuclei and negative electrons. These may be arranged along the lines of an
applied electric field E0. Formerly non-polar molecules get polarized and thus behave as
locally stationary dipoles. As can be seen in Fig. 2, the effects of the single dipoles cancel
each other macroscopically inside the dielectric. However, no partners with opposite charges
are present on the surfaces; these thus have a stationary charge, called a free charge. The free
charges in turn weaken the effective electric field Eas given below
𝑬 = 𝑬𝟎
sr (7)

Here 𝜀ris the dielectric constant (relative

permittivity) of the medium which is a
dimensionless, material specific constant.(𝜀r= 1 in
vacuum). If P is the polarization vector, the
induced electric field EP due to these charges will
be in opposite direction to applied electric filed:
− 𝑬 = sr–1𝑬
𝑬𝑷 = 𝑬𝟎 sr 𝟎
Fig.
= 𝑷 s0 2: Electric
(8)
field between

The electric displacement vector capacitor plates with a dielectric

for an isotropic
medium is defined as
𝑫 = 𝜺𝑬 = 𝜀O𝜀r𝑬 == 𝜀O𝑬 + 𝑷

(9)

where𝜀 is the electrical permittivity of the dielectric medium. When a dielectric is inserted
between the capacitor plates, according to Eq. (3), voltage Uc between the plates is reduced
by the dielectric constant, 𝜀r, as compared to voltage in vacuum (or to a good approximation,
in air). Since the real charge stored is constant, the capacitance will increase by a factor 𝜀r:
𝐶dieSectric= 𝜀r𝜀0
𝐴
(10)
𝑑
Thus the general form of Eq. 5 is

Q = 𝜀r𝜀0 𝑈𝑐 (11) 𝐴
𝑑
Experimental set up:
The actual experimental set up and a schematic of the same are shown in Fig. 3. In this
experiment the plate capacitors are charged using a high voltage supply. The charge stored
on it is transferred to a known capacitor Cref (220nF) by discharging the plate capacitor. The
voltage across Cref is fed to an electrometer amplifier and then measured using a voltmeter
as V0. From the reference capacitance Cref , the total charge, Q, stored on the capacitor is
obtained using the following equation and subsequently values of 𝜀r
for different media are determined using Eqns. 12 and 13.

DIAGRAM:

Precautions:

1. Take extreme care while operating with the high voltage supply.
2. Avoid touching of the plates while connected to high voltage supply.
3. Avoid synthetic clothing and maintain distance from the set up while performing
the experiment.
4. Use short cables as much as possible. Avoid loose connections.
EXPERIMENT 5

AIM : To determine the frequency and wavelength in a rectangular waveguide working in TE10
mode

REQUIREMENT :Klystron tube, Klystron power supply, Klystron mount, Isolator, Frequency
meter, Variable attenuator, Slotted section waveguide, Tunable probe, VSWR meter, Waveguide
stand, Movable short/matched termination.

THEORY :
For dominant TE10 mode in rectangular waveguide λ0, λg, and λc are related as below:

whereλois free space wavelength, λgis guide wavelength and λcis cutoff wavelength.

For TE10 mode, λc = 2a, where ‘a’ is the broad dimension of waveguide.

DIAGRAM:
EXPERIMENT 6

AIM :To measure unknown impedance with Smith Chart.

REQUIREMENT :
● Transmission line calculations.
● Smith Chart.
● Resistance and Reactance Circle on Smith Chart.
● Circle on Smith chart.

OBJECTIVE OF EXPERIMENT :

Transmission-line calculation – such as determination of input impedance, reflection and load impedance,
involve tedious manipulation of complex numbers. This tedium can be alleviated by using a graphical method
of solution. The best known and most widely used graphical chart is the Smith chart devised by P.H. Smith.
 Here Smith chart has been designed using LabVIEW programming for better understanding the concept behind
smith chart using graphical user interface.

This experiment gives an introduction to Smith chart and its application for the unknown impedance
measurement. From this experiment we will learn to use the Smith chart for transmission-line calculations.
This experiment will be helpful in learning following topics:

⮚ Realization of Smith chart and the basics of drawing a Smith chart.

⮚ Identification of resistance, reactance and VSWR circles on Smith chart.
⮚ Understanding the meaning of intersection of resistance and reactance circle over smith chart.
⮚ Representation of short-circuit and open-circuit points on Smith chart.
⮚ Identification of Admittance point, when load point is known.
⮚ Using a smith chart for the evaluation of the unknown impedance.

THEORY :

Smith Chart: Smith chart devised by P.H. Smith is the most widely used graphical chart for transmission line
calculations. It is a chart of resistance and reactance circles in the plane for where, r - and x- circles are
everywhere orthogonal to one another. The intersection of an r-circle and an x-circle defines a point that represents
normalized load impedance . This can be obtained on the LabVIEW programme by selecting option 3 from menu
and providing the values of r and x in the space specified. The actual load impedance is . Since a Smith chart
plots the normalized impedance for , it can be used for calculations concerning a lossless
transmission line only with arbitrary characteristic impedance.
DIAGRAM:
 and a
phase