Circuit lab 5 kirchoff’s voltage law (kvl)@taj . This lecture is from my class lectures in IIT-JU. . Find me: Website: https://www.tajimiitju.blogspot.com Linked in: https://www.linkedin.com/in/tajimiitju Researchgate: https://www.researchgate.net/profile/Tajim_Md_Niamat_Ullah_Akhund Youtube: https://www.youtube.com/tajimiitju?sub_confirmation=1 Slideshare: https://www.slideshare.net/TajimMdNiamatUllahAk Facebook: https://www.facebook.com/tajim.mohammad Gitlab: https://gitlab.com/users/tajimiitju Google+: plus.google.com/+tajimiitju Email: tajim.mohammad.3@gmail.com Twitter: https://twitter.com/Tajim53

1. Electronic Devices and
Circuits LAB (IT-1106)
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2. Circuit LAB 5:
Kirchoff’s
Voltage Law
Experiment 5
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Purpose/Objective:
To be familiar with the Kirchhoff’s
voltage and current laws.
To verify the KVL and KCL with the
help of simple series-parallel circuits
and hence to determine the equivalent
resistance of the circuits by
experimental and analytical methods.

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Theory
In 1845, a German physicist, Gustav Kirchhoff
developed a pair of laws which deal with the
conservation of current and energy within
electrical circuits. The rules are commonly
known as: Kirchoff’s Circuit Laws:
One law dealing with current flow around a
closed circuit, known as Kirchhoff’s Current
Law, (KCL)
Other law deals with the voltage around a
closed circuit, known as Kirchhoff’s Voltage
Law, (KVL).

5. Kirchhoff’s Voltage Law or KVL, states that-
“In any closed loop network, the total voltage
around the loop is equal to the sum of all the
voltage drops within the same loop" which is
also equal to zero.
In other words the algebraic sum of all
voltages within the loop must be equal to
zero.
This idea by Kirchhoff is known as the
Conservation of Energy.
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Kirchhoff’s Voltage Law, (KVL)
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Closed loop: A closed loop is a path in a circuit that doesn’t
contain any other closed loops. Loops 1 and 2 in Figure 1
are examples of closed loops.
Figure 1
KVL

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The perimeter of the circuit is also a closed loop, but since
it includes loops 1 and 2 it would be repetitive to include a
KVL equation for it. If loop 1 is followed clockwise the
KVL equation is:
V1 + V2 – Vs = 0 ------ (1)
This equation holds true only if the passive sign convention
is satisfied. In the case of KVL the passive sign convention
states that when a positive node is encountered while
following a loop the voltage across the element is positive.
If a negative node is encountered the corresponding
element voltage is negative. In order to simplify the KVL
equations, the polarities should be assigned to satisfy the
passive sign convention whenever possible.
KVL

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In the following figure, if KVL is applied then the equation is
Vs = V1+V2+V3 -------- (2)
Vs = IR1+IR2+IR3
Vs = I(R1+R2+R3) -------- (3)
Vs/I = Requivalent = R1+R2+R3 --------- (4)
Hence for series connections, we see from equation (4) that the
equivalent resistance is the algebraic sum of all individual
resistances.
KVL
Figure 2

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Equipment
a) One regulated variable Power Supply (0-30 V)
b) Two Digital Multimeter (One DC mili-ammeter,
one DC voltmeter)
c) Circuit Experiment Board (Breadboard)
d) Three resistors (10KΩ, 15KΩ and 20KΩ)
e) Connecting wires
f) Cutting tools etc.
KVL

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Cautions:
This equipment is delicate. Everything
should go together with the lightest of
touches. Do not force anything!
1. All connections should be tight and
correct.
2. Switch off the supply when not in use.
3. Reading should be taken carefully.
KVL

11. The circuit diagram to verify KVL is shown
below:
Figure-3: Circuit diagram for KVL verification
KVL

12. 1. Construct the circuit on the breadboard, as shown in figure-
3.
2. Start the experiment from the zero voltage of the power
supply. For zero supply voltage, the current flow is zero.
Now increase the supply voltage from 0 to 20 V in at least
five steps. For each step, take the ammeter and voltmeter
readings and check for V=V1+V2+V3.
3. Find the value of R1, R2 and R3 from color coding and from
direct ohmmeter readings. Algebraically add these three
resistances.
4. From the experimental readings of step 2, find the
equivalent resistance using equation (4) and compare it with
the result of step 3.
Procedure for KVL Verification
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Data Table for KVL Verification
KVL

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References:
1. Wikipedia
2. KMA sir’s lecture
3. Brad Peirson (2-24-05)
Results
Prove the equations:
Vs = V1+V2+V3 -------- (2)
And,
Vs/I = Requivalent = R1+R2+R3 --------- (4)
KVL

15. LAB Report
1. LAB report must
be hand written.
2. Report on today’s
LAB must be
submitted on next
class individually.
3. LAB report will
contain: topic, brief
description of the
topic, circuit
diagram, procedure,
data table,
equipment list and
graph.
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