Gauhati University.Lab Report

1. Department of Electronics and Communication Engineering
Gauhati University Institute of Science & Technology
Gauhati University, GNB Nagar,Ghy-14
LABORATORY REPORT
Electromagnetic Waves (ECE 311)
Name: Sunam Dutta
Roll no:190401001
Semester: 5th
Semester
Branch: Electronics and Communication

2. INDEX
Sl.
no.
Expt. No Title of Experiment Signature Remarks
1 1 To verify the relationship between the
voltage, the electric field and spacing of a
parallel plate capacitor
2 2 To measure the capacitance and
capacitance per unit length of a coaxial
cable of length 𝒍
3 3 To measure the inductance and inductance
per unit length of a coaxial cable of length 𝒍
4 4 To determine the characteristic impedance
of a coaxial cable of length 𝒍
5 5 To verify 𝑍2
= 𝑍𝑆𝐶.𝑍𝑂𝐶 for a coaxial
𝑂
transmission line

3. EXPERIMENT NO: 1
Aim of the Experiment: -
To verify the relationship between the voltage, the electric field and the
spacing of a parallel plate capacitor.
Required Equipment: -
a. Capacitor plate (2).
b. Electric Field Meter (1 KV/m=1mA).
c. Power Supply DC 12V and 250V (variable).
d. Multi-meters (2).
e. Plastic Ruler (100 cm).
f. Plastic and wooden sheet.
Theory: -
Assume one of the capacitor plates is placed in the y-z plane while the other is
parallel to it at distance ‘d’ as shown in figure
1. The effect of the boundary disturbance due to the finite extent of the plates is
negligible. In this case, the electric field intensity
𝐸 uniform and directed in x-direction. Since the field is
Irrotational it can be represented as the gradient of a scalar
field V.
which can be expressed as the quotient of differences

4. Where 𝑉𝐴 is the applied voltage and d is the distance between the plates. The
potential of a point at position x in the space between the plates is obtained by
integrating the following equation.
Experimental Setup: -

5. Procedure: -
a. The experimental setup is as shown in Figure 2. Adjust the plate spacing to
d= 10 Cm. The electric field meter should be zero-balanced with a voltage of
zero.
b. Measure the electric field strength at various voltages ranging from 0 to 250
V for d=10 cm and summarize the results in a table. Choose a suitable
voltage step to produce a smooth curve.
c. Plot a graph of the data of step (2). On the same graph paper, plot the
theoretical graph based on equation (2) and compare the theoretical and
experimental graphs.
d. Adjust the potential 𝑉𝐴 to 200V. Measure the electric field strength as the
plate separation is varied from d=2 cm to d=12 cm. Summarized our results
in a table.
e. Plot a graph of the data of step (4). On the same graph paper, plot the
theoretical graph based on equation (2) and compare the theoretical and
experimental graphs.
f. With a different medium (sheet) inserted between the plates, measure the
electric field strength at various voltages ranging from 0 to 30V. The
separation between the plates is fixed at d=1 cm. Repeat for all sheets.
Observation Table 1: -
Sl. No. Applied
Voltage(V)
Calculated Electric Field
(V/m)
1 0 0
2 12 120
3 24 240
4 48 480
5 96 960
6 192 1920
7 212 2120
8 250 2500

6. Observation Table 2: -
Sl. No. Applied Plate
Spacing (cm)
Calculated Electric Field
(V/m)
1 2 10000
2 4 5000
3 6 3333.3
4 8 2500
5 10 2000
6 12 1666.66
Conclusion: -
From the above experiment, electric field is calculated with variation of plate
separation (d) and Voltage (V).

7. EXPERIMENT NO: 2
Aim of theExperiment: -
To measure the capacitance and capacitance per unit length of a co-axial
cable of length 𝒍.
Equipment Required: -
1. LCR meter
2. A length of coaxial cable
3. Vernier Caliper
Theory: -
Foraco-axialtransmissionline,thecapacitanceperunitlength is givenby
andC is the capacitance
of the coaxial line of length l.
Procedure: -
1. Connect the positive terminal of the LCR meter with the inner conductor of
coaxialcableatoneend.
2. Connect the negative end of the LCR meter to the outer conductor of the
coaxialcableatthesameend.
3. Leave the outer end unconnected and put the setting of LCR to measure capacitance
andnotthereading(c).
4. Measurethelength of thecable (𝒍).
5. Thecapacitanceperunitlengthisgivenby
𝑐
𝑙
6. Measure‘a’ and‘b’ usingVernier caliper.

8. Observation Table: -
Sl. No. L(m) a(mm) b(mm) c(farad) 𝑐
𝑙
1 2 7 10 3.1×10−12
1.55×10−12
2 4 12 15 9.92×10−10
2.48×10−10
3 6 17 20 2.04×10−9
3.41×10−10
4 8 22 25 3.47×10−9
4.43×10−10
5 10 27 30 5.27×10−9
5.27×10−10
Conclusion: -
From the above experiment we have calculated the value of capacitance per unit length by
measurement of length l, the diameter of transmission line a & b.

9. EXPERIMENT NO: 3
Aim of the Experiment: -
To measure the inductance and inductance per unit length coaxial
cable of length 𝒍.
Equipment Required: -
1. LCR meter
2. A length of coaxial cable
3. Vernier Caliper
Theory: -
For a co-axial transmission line, the inductance per unit length is given by
inductance of the coaxial line of length 𝒍.
Procedure: -
1. Connect the positive terminal of the LCR meter with the inner conductor of
coaxial cable at one end.
2. Connect the negative end of the LCR meter to the outer conductor of the
coaxial cable at the same end.
3. Leave the other end unconnected and put the setting of LCR to measure
inductance and not the reading.
4. Measure the length of the cable (𝒍).
5. The inductance per unit length is given by
𝑐
𝑙
6. Measure ‘a’ and ‘b’ using Vernier Caliper

10. Observation Table: -
Result: -
From the above experiment, we can measure the inductance and inductance per
unit length of a co-axial cable of length.

11. EXPERIMENT NO: 4
Aim of the Experiment: -
To determine the characteristics impedance of a coaxial cable of length 𝒍.
Equipment Required: -
1. LCR meter
2. A length of coaxial cable
3. Vernier Caliper
Theory: -
For a co-axial transmission line, the characteristics impedance of a transmission is given
by
Where, is the inductance of the co-axial line of length
Procedure: -
1. Connect the positive terminal of the LCR meter with the inner conductor of
coaxial cable at one end.
2. Connect the negative end of the LCR meter to the outer conductor of the
coaxial cable at the same end.
3. Leave the other end unconnected and put the setting of LCR to measure
impedance and not the reading.
4. Measure the length of the cable (𝒍).
5. The capacitance per unit length is given by
𝑪
𝒍
6. The inductance per unit length is given by
𝒄
𝒍
7. Measure ‘a’ and ‘b’ using Vernier Caliper

12. Observation Table: -
Conclusion: -
From the above experiment we have calculated the value of characteristic of impedance
by measurement of length l, the diameter of transmission line a & b.

13. o SC OC
EXPERIMENT NO: 5
Aim of the Experiment: -
Toverify Z 2
=Z .Z foracoaxialtransmissionline
Required Equipment’s: -
1. LCR Meter
2. A length of co-axial cable
3. Vernier caliper
4. A function generator
Theory: -
The input impedance of a lossless transmission line terminated by a
load ZL is given by
𝑍𝑖𝑛 =𝑍𝑜
𝑍𝐿+𝑗𝑍𝑜 tan 𝛽𝑙
𝑍𝑜+𝑗𝑍𝑙𝑡𝑎𝑛𝛽𝑙
Where 𝑍𝑜 is the characteristic impedance
𝒍 isthelengthofthetransmissionline
𝛽 isthephaseconstant
The Open circuited load input impedance is denoted by
𝑍𝑜𝑐 and it is the input impedance of the transmission line when the load end is
open circuited.

14. The input impedance of the transmission line when the load end is
shorted and is denoted by 𝑍𝑠𝑐. If 𝑍𝑜 is the characteristic impedance of a
lossless transmission line, then
where
𝑍𝑠𝑐 = 𝑗𝑍𝑜 tan𝛽𝑙
𝑍𝑜𝑐 = −𝑗𝑍𝑜cot𝛽𝑙
Procedure: -
1. Determine the characteristic impedance of the transmission line by
following the steps mention in the experiment no. 4.
2. Short the load end of the transmission line after making a circuit
connection shown as in fig (1).
3. Use LCR meter to measure the input impedance of the transmission line
by connecting it to the generator end of the transmission line.
4. Open circuit the load end of the transmission line and connect the
LCR meter to the generating end of the transmission line.
5. Set the LCR meter for impedance measurement and note down the 𝑍𝑜𝑐
Value.
6. Check if
Observation: -
Consider β=2rad/sec
Conclusion: -
From the above experiment, we verified
for a coaxial transmission line.
Sl. No 𝒍 𝒁𝒐
𝟐 Zsc. Zoc 𝒂 𝒃
1 10 539.971 539.971 1 5
2 20 2453.916 2453.916 3 7
3
30 319.280 319.280 5 9