Investigatory Project
Topic: Studying the Operation of the Wheatstone Bridge Circuit and its Use
Submitted By: ___________________
Class: IX
Subject: Science / Physics
Certificate
This is to certify that ___________________ of Class IX has successfully completed the
investigatory project titled “Studying the Operation of the Wheatstone Bridge Circuit and
its Use” under my guidance.
Teacher’s Signature: ___________
Acknowledgement
I would like to express my sincere gratitude to my teacher for guiding me throughout this
project. I am also thankful to my parents and friends for their continuous support and
encouragement.
Index
S. No. Content
1 Introduction
2 Aim of the Project
3 Theory / Principle of Wheatstone Bridge
4 Materials Required
5 Circuit Diagram
6 Procedure
7 Observations
8 Calculations
9 Results
10 Applications
11 Advantages & Limitations
12 Precautions
13 Conclusion
14 Bibliography
Introduction
The Wheatstone Bridge is a fundamental electrical circuit used to measure unknown
resistances accurately. It was invented by Samuel Hunter Christie in 1833 and later
popularized by Sir Charles Wheatstone in 1843. The bridge is based on the principle of null
deflection, which means that when the bridge is balanced, no current flows through the
galvanometer.
Aim of the Project
To study the operation of the Wheatstone Bridge circuit and understand its applications in
measuring electrical resistance.
Theory / Principle
The Wheatstone Bridge consists of four resistors arranged in a diamond shape. A
galvanometer is connected between two opposite points, and a battery is connected across
the other two points. The bridge works on the principle of a balanced network. When the ratio
of resistances in one arm is equal to the ratio in the other arm, the galvanometer shows zero
deflection, indicating a balanced condition. Mathematically, the balance condition is given by:
R1 / R2 = R3 / R4
Materials Required
1. Resistors (known and unknown) 2. Battery (DC source) 3. Galvanometer 4. Connecting
wires 5. Rheostat (if required) 6. Breadboard or circuit board
Circuit Diagram
[A neat labeled diagram of Wheatstone Bridge is to be drawn here.]
Procedure
1. Connect the circuit as per the Wheatstone Bridge arrangement. 2. Place the unknown
resistance in one arm of the bridge. 3. Adjust the known resistances and note the
galvanometer deflection. 4. Change the resistance until the galvanometer shows zero
deflection. 5. Record the values of resistances in all arms of the bridge. 6. Apply the
Wheatstone Bridge principle to calculate the unknown resistance.
Observations
Sample observation table: Known Resistance (R1): ___ Ω Known Resistance (R2): ___ Ω
Variable Resistance (R3): ___ Ω Unknown Resistance (R4): To be calculated
Calculations
From the balance condition of the Wheatstone Bridge: R1 / R2 = R3 / R4 Thus, Unknown
Resistance R4 = (R2 × R3) / R1
Results
The unknown resistance was found to be: ______ Ω
Applications
1. Measurement of unknown resistance with high accuracy. 2. Used in strain gauge
measurements for stress analysis. 3. Used in sensor applications such as temperature
sensors. 4. Forms the basis of modern electrical measuring instruments. 5. Useful in
calibration of measuring devices.
Advantages
1. High accuracy in measurement. 2. Simple experimental setup. 3. Easy to calculate
unknown resistances. 4. Can be used in various scientific experiments.
Limitations
1. Not suitable for measuring very low resistances. 2. Errors due to heating of resistors. 3.
Galvanometer sensitivity affects accuracy. 4. Requires a stable power source.
Precautions
1. Ensure all connections are tight and free from rust. 2. Use a sensitive galvanometer for
accurate results. 3. Do not allow high current through the galvanometer. 4. Perform the
experiment on an insulated surface. 5. Avoid parallax error while noting readings.
Conclusion
The Wheatstone Bridge is an important tool for measuring resistance. By balancing the bridge
and applying the balance equation, the value of an unknown resistance can be determined
accurately. This principle finds applications in both educational experiments and advanced
technological devices.
Bibliography
1. NCERT Science Textbook, Class IX 2. Concepts of Physics – H.C. Verma 3. Internet
sources (educational websites) 4. Reference notes provided by school teachers
