Electronic Engineering Circuit II
(Lab Instruction and Lab Report)
EcE 22001
Capacitor
Ceramic Capacitor
Mica Capacitor
Tantalum Capacitor
Polyester film C
Aluminum electrolytic C
Electric double layer C
Symbol
Purpose
1.
2.
3.
4.
Temporary electrical energy storage
AC and DC separation and selection
Phase shift between voltage and current
Signal differentiation and integration, etc.
(1)
(2)
2
Polypropylene film C
(3)
(4)
Molded Paper Capacitor Codes (Capacitance given in pF)
Color
Digit
Multiplier
Tolerance
Black
0
1
20%
Brown
1
10
Red
2
100
Orange
3
1000
Yellow
4
10000
Green
5
100000
Blue
6
1000000
Violet
7
Gray
8
White
9
5%
10%
Gold
5%
Silver
10%
No Color
20%
3
Experiment No.1 Reading Capacitor
Example
st
11st
2nd
3rd
Capacitance Value Number
Capacitance Value Number
Number of Zero
101 = 100 PF (or) 0.0001 μF
102 = 1000 PF (or) 0.001 μF
473 = 47000 PF (or) 0.047 μF
Table
Colour Bands
Farad (F)
1
2
3
4
5
6
4
Tolerance
(±%)
Experiment No. 2 Testing Capacitor
Objective
Upon the completion of this activity, the student must be able to check whether a
capacitor is good or not.
Material
- Polarized capacitors
- Non-polarlized capacitors
- Multimeter (Ohmmeter)
Procedure
Polarized Capacitors
1. Connect the two terminals until no charge in the capacitor (momentarily discharge). OR
Connect about 1k at one terminal.
2. Set the range switch at the lowest Ohm scale (×1).
3. Connect the meter positive probe with the positive terminal of capacitor and so do the rest
terminals.
4. The pointer goes to ‘zero’ and then back to its initial values if capacitor is good.
5. If the pointer goes to ‘zero’ and stands still at that point, the capacitor is short circuited.
6. If the pointer does not show any movement, the capacitor is in open circuited.
7. As the pointer goes to zero and then back to not its initial values, there is leakage in the
capacitor.
Non-polarized Capacitor
1. Set the range switch at ×100 Ohm scale.
2. Testing procedures are as the previous ones.
5
Inductor
Figure
Symbol
Purpose
1.
2.
3.
4.
Temporary energy storage
AC and DC separation and selection
Phase shift between voltage and current
Magnetic field generation, etc.
(1)
(2)
6
(3)
(4)
Experiment No.3
SERIES AC CIRCUITS
Objectives :

To prove any phase angle between 0 ° and 90° can be achieved with an inductor or
capacitor and a given resistance value

To measure voltage and current in various kinds of series AC circuit

To draw the vector diagrams
Computer-Aided Circuit Analysis (Using Multisim Software)
a. Draw the circuit diagram
b. Measure the current
c. Measure the voltage
Theory
(1) Circuit with pure resistance only:
When sinusoidal alternating current i=Imaxsint flow though a non-inductive resistor
R ohms, the instantaneous voltage across the resistor is
e = Emax sint
ER = Emax /√2 and IR = Imax / √2
where ER and IR are the r.m.s value of voltage and currents.
The vector diagrams are usually drawn with r.m.s quantities. For the non-inductive
resistor the voltage and current are in phase.
I
R
ER
I
ER
Fig.
(2) Pure inductance
If i=Imaxsint flows through a pure inductance of L henery, then is a back e.m.f
induced which tends to oppose the change in current.
EL = LImaxcost = LEmaxsint
here XL = L = inductance in ohms. Thus EL leads I by 90.
7
EL
I
L
EL
I
Fig.
(3) Inductance with internal resistance r
In the case of a choke, which contain inductance and a small resistance, then the
vector diagram is as shown in Fig. Thus voltage across the choke, i.e E L leads I by angle 
which is less than 90.
EL
I
R
L
ER
EL
E
I
ER
Fig.
(4) Pure capacitance
If a voltage EC = Emaxsint is applied to a capacitor of C farads, the current
i = Imaxsin(t+90) will flow
1/C = XC , capacitive reactance in ohms
Thus the current I lead the voltage EC by 90 as shown in Fig.
I
I
C
EC
EC
Fig.
(5) Series circuit containing resistance, inductance and capacitance.
I
R
L
r
ER
EL
E
Fig.
8
C
EC
EL
E
I
ER
ER+EC
EC
Fig.
We have Z = E/I where Z is the impedance of the circuit in ohms.
(𝑅/𝑟)2
Also, Z = √(𝑋
2
𝐿 /𝑋𝐶 )
Note: When drawing the vector diagram for series circuit, always draw the current
vector first since it is common to all the components. Hence I is known as the reference
vector.
Procedure (1)
Connect the resistor and choke in series to a 24 V, 50 Hz supply as shown in Fig.
Measure the current I and three voltages: (a) voltage across the choke-series ET. (b) voltage
across the choke EL and (c) voltage across the resistor ER
ER
EL
A
L
R
24
ET
Fig.
Fig.
9
r
Table. Simulation Result
ER
EC
ET
I
V(r.m.s)
V(r.m.s)
V(r.m.s)
mA(r.m.s)
ER
EC
ET
I
V(r.m.s)
V(r.m.s)
V(r.m.s)
mA(r.m.s)
Table. Practical Result
Draw the vector diagram for this procedure. Calculaate R, XL, Z and power factor.
(assume that the internal resistance of the choke is ---------- ohms)
10
Procedure (2)
Connect the resistor and capacitor in series to the power supply as shown in Fig.
Measure the current I and three voltage actoss viz: (a) voltage across the capacitor-resistor
series ET, (b) voltage across the capacitor EC and (c) voltage across the resistor ER.
ER
A
R
24V
ET
EC
C
Fig.
Fig.
Table. Simulation Result
ER
EC
ET
I
V(r.m.s)
V(r.m.s)
V(r.m.s)
mA(r.m.s)
11
Table. Practical Result
ER
EC
ET
I
V(r.m.s)
V(r.m.s)
V(r.m.s)
mA(r.m.s)
Draw the vector diagram for the procedure. Calculate R, XC, Z and power factor.
12
Procedure (3)
Connecte the resistor, choke and capacitor in series to the power supply as shown in
Fig. Measure the current I and three voltage across viz: (a) total voltage ET, (b) voltage across
the resistor ER and (c) voltage across the choke EL and (d) voltage across the capacitor EC
I
E
EC
R
C
EL
A
L
r
E
Fig.
Fig.
Table. Simulation Result
E
EL
EC
I
ET
V(r.m.s)
V(r.m.s)
V(r.m.s)
mA(r.m.s)
V(r.m.s)
13
Table. Practical Result
E
EL
EC
I
ET
V(r.m.s)
V(r.m.s)
V(r.m.s)
mA(r.m.s)
V(r.m.s)
Draw the vector diagram for these voltages. Calculate R, XL, XC and power factor.
14
Experiment No.4
PARALLEL AC CIRCUITS
Objectives :

To determine by experiment the resonant frequency of a parallel LC circuit.

To measure voltage and currents in all kinds of parallel AC circuits and to draw the
vector diagrams.
Computer-Aided Circuit Analysis (Using Multisim Software)
a. Draw the circuit diagram
b. Measure the current
c. Measure the voltage
The phasor voltage and phasor current of the resistor are inphase. The phasor voltage
and phasor current of the capacitor are 90 out of phase. (current lag voltage by 90) The
phasor voltage and phasor current of the inductor are 90 out of phase. (current lead voltage
by 90)
IS
IR
IC
R
C
E
Fig.
IS
IC
IR
E (Reference)
Fig. Vector Diagram
15
Procedure (1)
Connect the resistor and capacitor in parallel across the 24V, 50Hz supply. Measure
the supply voltage E and three currents viz: (a) supply current Is (b) resistor current IR (c)
capacitor current IC.
E
IR
IC
IS
V(r.m.s)
mA(r.m.s)
mA(r.m.s)
mA(r.m.s)
Consider now a parallel combination of resistor, choke and capacitor as shown in Fig.
A coil of 30 mH, a resistor of 10, and a capacitor of 350F are connected in parallel and
supplied by a 120 V 60Hz generator.
IS
IR
IL
IC
L
R
C
E
r
Fig.
Fig.
where r = the internal resistance of the choke
16
KCL at upper node in Fig,
IS = IR + IL + IC
The vector diagram is shown in Fig.
IC+IR
IC
IR
E (Reference)
IS
IL
Fig. Vector Diagram
Procedure (2)
Connect the resistor and choke and capacitor in parallel across the 24V, 50Hz supply
as shown in Fig. Measure the supply voltage E and four currents viz: (a) supply current IS (b)
resistor IR, (c) choke current IL and (d) capacitor current IC.
Table. Simulation Result
E
IR
IL
IC
IS
V(r.m.s)
mA(r.m.s)
mA(r.m.s)
mA(r.m.s)
mA(r.m.s)
E
IR
IL
IC
IS
V(r.m.s)
mA(r.m.s)
mA(r.m.s)
mA(r.m.s)
mA(r.m.s)
Table. Practical Result
Question 1
Draw the vector diagram for these currents. Determine the power factor and total impedance.
17
Question 2
Consider the parallel combination of a capacitor and an inductor (choke). Connected the
resistor and choke in parallel across the 24V, 50Hz supply. Measure the supply voltage E and
three current viz: (a) supply current Is, (b) resistor current IR, and (c) choke current IL.
E
IR
IL
IS
V(r.m.s)
mA(r.m.s)
mA(r.m.s)
mA(r.m.s)
Draw vector diagram for this procedure. Calculate R, XL, Z and power factor.
(Assume that the internal resistance of the choke = --------------.)
Vector diagram and Calculation
18
Experiment No.5
SERIES RESONANCE CIRCUITS
Objectives :

Learn the definition of resonance in AC circuits.

Learn to calculate resonant frequencies, band widths, and quality factors for series and
parallel resonant circuits.

To investigate futher the series RLC circuit, especially around the point of minimum
impedance
Computer-Aided Circuit Analysis (Using Multisim Software)
A series resonance circuit is composed of the elements R = 1k, L = 140mH, and C = 0.27
F. Adjust the function generator to give 10V at 600 Hz.
a. Draw the circuit diagram
b. What is the calculated value of resonance frequency?
c. Measure the current, voltage across the inductor and capacitor.
d. Increase for the frequencies given in table with 10 V rms from function generator
and take the readings of I, VL, VC.
e. Find the resonance frequency (where |I| is maximum) again and take a set of
reading at this frequency.
f. Does the calculated value of fo agree with the value obtained from simulation
experiment.
g. What is the value of |VL| and |VC| at fo
Experimental Procedure
Connect up the circuit as shown in the circuit diagram of Fig.
19
V
E
F
G
L
R
Function
Generator
H
C
A
Fig.
Fig.
Connected the voltmeter across the input to the circuit (point marked E and H on Fig
and adjust the generator output to give 10 Vrms at 600 Hz.
Vary the frequency of the generator from about 600 Hz to 1000 Hz and note the
variation in current and voltage.
Find the frequency at which the current impedance is a minimum. This is where the
current is a maximum and the voltage is a minimum.
Question (1) What is the frequency?
This frequency is termed the Resonant Frequency of the circuit. At the
resonant frequency of the circuit the capacitive reactance is equal to the inductive reactance,
and they cancel each other out. The circuit impedance at the resonant frequency is thus just
the resistance of the circuit.
Measure the current and voltage at resonance and calculate the impedance at
resonance.
20
Question (2) Does the calculated value agree with the value expected?
1
𝑋𝐶 = 2𝜋𝑓𝐶
𝑋𝐿 = 2𝜋𝑓𝐶
At resonance |𝑋𝐶 | = |𝑋𝐿 |
1
Thus,
2𝜋𝑓𝐶
= 2𝜋𝑓𝐿 at resonance
Let us denote the resonant frequency by the symbol fo
1
Then,
2𝜋𝑓𝐶
= 2𝜋𝑓𝐿
4𝜋 2 𝑓 2 𝐿𝐶 = 1
1
𝑓 = 𝑓𝑜 = 2𝜋√𝐿𝐶
From this derive an expression for fo in terms of L and C.
Question (3) fo = ------------- Hz?
Substitute L = 140mH, C = 0.27F in the expression and workout fo
fo = ------------- Hz
Question (4) Does the calculated value agree with the frequency found previously for
minimum impedance?
Set the generator frequency to 600 Hz and the ouput voltage to 10 Vrms. Take
is reading of the circuit |I|, the inductor voltage |VL| and the capacitor voltage |VC|. Record the
readings in the Table.
Table. Simulation Result
Frequency
Input Voltage
Current
f(Hz)
Vin(V)
I(mA)
600
650
700
750
760
780
790
800
810
21
VC(V)
VL(V)
820
830
850
900
950
Table. Practical Result
Frequency
Input Voltage
Current
f(Hz)
Vin(V)
I(mA)
VC(V)
VL(V)
600
650
700
750
760
780
790
800
810
820
830
850
900
950
Increase the frequency to 650 Hz and readjust the generator output to give 10 Vrms
again.
Take readings of V, I, VL and VC as before.
Reapeat the procedure for the frequencies given the table.
Ensure that the load voltage is 10 Vrms for each frequency setting. Find the resonant
frequency again (the frequency at which the current is a maximum) and take a set of readings
at this frequency, fo.
On a graph paper, draw curves of I, VL and VC, against frequency.
Remove the resistor from the ciruit and connect points E and F together. Set the
generator frequency back 600 Hz, set the ouput amplitude to 10 Vrms. Take measurements as
before and insert the data in Table.
22
Frequency
Input Voltage
Current
f(Hz)
Vin(V)
I(mA)
VC(V)
VL(V)
On graph paper plot the second set of I, VL and VC curves.
Notice the differing shapes of the two sets of curves.
Question (5) From the curves plotted with R = 1 k in circuit, what is the resonant
frequency of the circuit (where |I| is a maximum)?
Question (6) What is the vlaue of |I| at this frequency?
Question (7) What is the value of |VL| at fo?
Question (8) What is the value of |VC| at fo?
𝑉
𝑉
The ratio of 𝑉 𝐿 or 𝑉 𝐶 at fo is termed the Quality Factor, Q.
𝑖𝑛
𝑄=
𝜔𝑜 𝐿
𝑅
𝑖𝑛
𝑜𝑟
1
𝜔𝑜 𝐶𝑅
Let us now examine the graphical results for the circuit with R removed.
Question (9) What is the resonant frequency?
Question (10) Does it differ from fo when R = 1 k?
23
Question (11) What are the value of I, VC, VL at fo?
Let us now shapes of the curves.
At resonance I is a maximum and as I = Vin/Z then Z must be a minimum.
Thus we sometimes call a series RLC circuit an ‘asseptor circuit’ because its impedance to
a.c signal about its resonant frequency is low, where it presents high impedance to other
frequencies. The RLC circuit will thus pass signal near to its resonant frequency much more
readily than those of other frequencies. It is said to have a ‘band pass’ effact.
By examinig the two sets of curves it can be seen that the current curve when R = 0 is
much shaper in its peaking than when R = 1k. It follows that the ‘band’ or range of
frequencies accepted by the circuit with the shaper peaked current curve will be narrower
than fof the flatter one.
We say that the ‘bandwidth’ of the circuit with R = 0 is smaller than that with R =
1k. Bandwidth is defined as the change in frequency between the point on the current curve
which are 0.707 of the current at resonance. This is shown in Fig.
BW = (f2 – f1)Hz
here BW = Bandwidth of the resonance circuit (Hz)
Insert the data from the above two experiments in Table and calculate the bandwidth.
Imax(mA)
0.707Imax
f1(Hz)
f2(Hz)
f2 – f1 (Hz)
for R = 1k
for R = 0
We see than that a circuit with a low value of Q has a large bandwidth and one with a
higher Q has a smaller bandwidth.
24
Experiment No.6
PARALLEL RESONANCE CIRCUITS
Objectives :

to determine by experiment the resonant frequency of a parallel LC circuit.

Learn the definition of resonance in AC circuits.

Learn to calculate resonant frequencies, band widths, and quality factors for series and
parallel resonant circuits.
Computer-Aided Circuit Analysis (Using Multisim Software)
A parallel resonance circuit is composed of the ideal elements R = 10k, L = 1mH, and C =
1 F. Use the ac current source of 10 mA with frequency 5.03k Hz.
a. Draw the circuit diagram
b. What is the calculated value of resonance frequency?
c. Measure the current across the inductor and capacitor at resonance frequency.
d. Measure the voltage VC at resonance.
e. Calculate the quality factor and bandwidth of the system.
Experimental Procedure
Fig.
25
Table. Simulation Result
Current
Source
Resonance
Frequency
VC at fp
IC at fp
IL at fp
VC at fp
IC at fp
IL at fp
(fp)
Quality Factor
Bandwidth
(Qp=R1/2fpL)
(BW = fp/Qp)
Quality Factor
Bandwidth
(Qp=R1/2fpL)
(BW = fp/Qp)
10 mA,
1kHz
20 mA,
1kHz
10 mA,
5.03kHz
1 mA,
5.03kHz
10 mA,
10kHz
Table. Practical Result
Current
Source
Resonance
Frequency
(fp)
10 mA,
1kHz
20 mA,
1kHz
10 mA,
5.03kHz
1 mA,
5.03kHz
10 mA,
10kHz
26