# -Kirchoff-s-law ```PHYSICS INVESTIGATORY PROJECT
2019-20
AIM:
To verify the Kirchhoff’s laws by applying them to cubical
circuits to find their equivalent resistance.
Subject Teacher:-Sandeep Kaur
Submitted by:-Manish Kumar
Board RollNO :- __________________
INDEX
Certificate of Excellence
Acknowledgement
Introduction
Apparatus
Theory
Procedure Followed
Observation
Precaution
Sources Of Error
Bibliography
CERTIFICATE
This is to certified that Manish Kumar, a student of class
XII-D has successfully completed the research on the
below mentioned project under the guidance of
SANDEEP KAUR(subject teacher) and our physics lab
expert MR. SATISH during the year 2018-19 in partial
fulfillment of physics practical examination conducted by
CBSE.
Signature of Physics Teacher
ACKNOWLEDGEMENT
In the accomplishment of this project successfully,
many people have best owned upon me their blessings
and the heart pledged support, this time I am utilizing
to thank all the people who have been concerned with
project.
Primarily I would thank god for being able to complete
this project with success. Then I would like to thank my
principle MRS. ANITA AGGARWAL, physics teacher
MRS.SANDEEP KAUR and our physics lab expert MR.
SATISH whose valuable guidance has been the once
that helped me patch this project and make it full proof
success. Their suggestions and their instruction have
served as the major contributor towards the
completion of the project.
Then I would like to thank my parents and friends who
have helped me with their valuable suggestion and
guidance has been helpful in various phases of the
completion of project.
Last but not least I would like to thank my classmate
who has helped me a lot.
INTRODUCTION
A Resistance Cube is one which is made up of
resistances connected to the each side of the cube.
It is also known as Kirchhoff’s Cube. This cube
contains three different positions for finding the
equivalent resistance of the cube.
The Positions are: Ends connected in body diagonals
 Ends across face diagonal
 Ends across the vertices of the cube
APPARATUS
1. Ammeter
2. Resistance wires
3. Voltmeter
4. Keys
5. Rheostat
6. Battery
7. Connection wires
8. Meter scale
KIRCHOFF’S LAW (FIRST LAW)
JUNCTION RULE:
At ant node (junction) in an electrical circuit the sum
of currents flowing into that is equal to the sum of
currents flowing out of that node, the algebraic sum
of currents in a network of conductors meeting at a
point is zero.
The formula is valid for complex currents.
This law is based on the conservation of charge is the
products of the current and the time.
KIRCHOFF’S LAW(SECOND LAW)
LOOP RULE:
It is based on the principle of conservation of energy.
It states that in any closed loop the sum of the
potential droops across the resistors is equal to the
E.M.F of the cell.
Formula:
This law is based on the conservation of energy
where by voltage is defined as they energy per unit
charge must be equal to the amount of energy and
charge are both conserved.
PROCEDURE
Take equal length of resistance wire and wound them
over a cube of desired edge length.
Using ohms law apparatus, find the resistance of
each circuit as explained below.
Note: That voltmeter and ammeter readings. On dividing
the former be latter, we get resistance of experimental
circuit.
COLOUR CODING
A colour code is used to indicate the resistance value of a
carbon resistor and its percentage accuracy.
 A set of coloured co-axial rings or bands is printed on
the resistor which reveals the following facts.
The first band indicates the first significance figure.
The second band indicates the second significance
figure.
The third band indicates the power with which the
above two significant figure must be multiplied to
get the resistance value in ohm’s.
The fourth band indicates the tolerance or the
possible variation of the indicated value. If the
fourth band is absent, it implies a tolerance of 20%.
ACROSS BODY DIAGONAL
CUBE-1
Edge of cube________
Voltage(V)
Current(A)
Resistance(OHMS)
MEAN R=________Ω
Rne t = (5/6)R=________Ω
CUBE-2
Edge of cube ________
Voltage(V)
Current(A)
MEAN R=________Ω
Resistance(OHMS)
Rne t = (5/6)R=________Ω
CUBE-3
Edge of cube ________
Voltage(V)
Current(A)
MEAN R=________Ω
Rne t = (5/6)R=________Ω
PERCENTAGE ERRORS
Cube-1
Cube-2
Resistance(OHMS)
Cube-3
ACROSS FACE DIAGONAL
CUBE-1
Edge of cube________
Voltage(V)
Current(A)
Resistance(OHMS)
MEAN R=________Ω
Rne t = (3/4)R=________Ω
CUBE-2
Edge of cube ________
Voltage(V)
Current(A)
Resistance(OHMS)
MEAN R=________Ω
Rne t = (3/4)R=________Ω
CUBE-3
Edge of cube ________
Voltage(V)
Current(A)
MEAN R=________Ω
Rne t = (3/4)R=________Ω
PERCENTAGE ERRORS
Cube-1
Cube-2
Resistance(OHMS)
Cube-3
ACROSS THE VERTICES OF AN EDGE
CUBE-1
Edge of cube________
Voltage(V)
Current(A)
Resistance(OHMS)
MEAN R=________Ω
Rne t = (7/12)R=________Ω
CUBE-2
Edge of cube ________
Voltage(V)
Current(A)
Resistance(OHMS)
MEAN R=________Ω
Rne t = (7/12)R=________Ω
CUBE-3
Edge of cube ________
Voltage(V)
Current(A)
MEAN R=________Ω
Rne t = (7/12)R=________Ω
PERCENTAGE ERRORS
Cube-1
Cube-2
Resistance(OHMS)
Cube-3
OBERVATIONS
Least count of Voltmeter__________
Least count of Ammeter___________
Voltage(V)
Current(A)
MEAN R=________Ω
Resistance:


RESULT
Resistance(OHMS)
PRECAUTIONS
Key should not be inserted when reactions are to be
taken.
The resistance should be equal length.
All connections should be made tight.
Connecting wires should be properly rubbed with sand.
SOURCES OF ERROR
The resistivity of the wire is not accurate.
Connections may not be tight.
High voltage may be used due to which short circuit
may occur.
BIBLIOGRAPHY
Class XII-Physics NCERT-Part 1.
Wikipedia.com