REPORT OF BASIC PHYSICS EXPERIMENT 2 WHEATSTONE BRIDGE
Yuanita Sri Respati K2312080
Physics Education 2012 A
TEACHER TRAINING AND EDUCATION
SEBELAS MARET UNIVERSITY
Acknowledgements
List of contents
1. Acknowledgements………...1
2. List of contents………..2
3. List of figures/tables……….....2
4. Introduction………..3
1. The abstract………..3
2. Statement of the Problem……….3
5. Main body……….4
1. Review of literature……….…4
2. Design of the investigation……….…6
3. Measurement techniques used………6
4. Results………7
6. Conclusion………9
1. Discusion and conclusion………9
2. Sumary of conclusion……….10
7. Reference………11
List of figures/tables 1. Table of resistivities of various materials………(5)
2. Table magnitude of resistance……….(7)
3. Table the magnitude of copper wire resistivity………...(7)
4. Table the magnitude of nicel wire resistivity……….………….(8)
Introduction
1. The abstract
The purpose experiment were to measure value of resistance and value of resistivity nicel wire and copper wire. The method to measure value of resistance was move of move contact in wheatstone bridge circuit and to measure value of resistivity replaced Rx with nicel wire and copper wire, galvanometer used to detect electrict current. This experiment used standart deviation. The result value of resistance was (5.21 ± 0.39)Ω, value of resistivity copper wire was (8.78 ± 2.70)10−8Ω𝑚 and value of resistivity nicel wire was (9.40 ± 1.40)10−8Ω𝑚.
Key word: resistance, resistivity.
2. Statement of the Problem
A Wheatstone bridge was an electrical circuit used to measure an unknown electrical resistance by balancing two legs of a bridge circuit, one leg of which included the unknown component. Its operation was similar to the original potentiometer. It was invented by Samuel Hunter Christie in 1833 and improved and popularized by Sir Charles Wheatstone in 1843. One of the Wheatstone bridge's initial uses was for the purpose of soils analysis and comparison.
The Wheatstone bridge illustrated the concept of a difference measurement, which can be extremely accurate. Variations on the Wheatstone bridge can be used to measure capacitance,inductance, impedance and other quantities, such as the amount of combustible gases in a sample, with an explosimeter. The Kelvin bridge was specially adapted from the Wheatstone bridge for measuring very low resistances. In many cases, the significance of measuring the unknown resistance is related to measuring the impact of some physical phenomenon (such as force, temperature, pressure, etc.) which thereby allows the use of Wheatstone bridge in measuring those elements indirectly.
Main body
1. Review of literature
Resistance (R) is defined as the ratio of the voltage (V) applied cross a piece of material to the current (I) through the material, or 𝑅 = 𝑉
𝐼
The resistance is a constant and the relation 𝑅 =𝑉
𝐼 is refered to as Ohm’s Law.
(John. D. Cutnell & Kenneth W John, 1989, 520) A single-loop circuit is a circuit with a single path for the current. the net potential change in traversing the complete circuit is zero simply due to the conservation of energy. If we had followed the circuit in the opposite direction againts the current-the changes would all be of the opposite sign, but the end result would remain: the potential change in a complete circuit is zero. In the context of circuit this simple law is given a special name , Kirchhoff’s loop rule.
𝛴∆𝑉 = 0
I steady-state operation, the current moving along a wire in an electric circuit ia constant. If it were not, charge would build up at some point and change the electric field-in disagreement with our assumption of a steady state. This conservation of current also holds at a circuit junction where three or more wires come together. We know that charge is conserved, so at any given time, the rate at which charge enters a
junction is equal to the rate at which charge leaves the junction. Kirchhoff’s junction
rule (also know as kirchhoff’s first law) states that the sum of the current that enter a
junction equals the sum of the current that leave the junction. We can state this another way: if we interpret a current that leaves a junction as the negative of a current of the same magnitude that enters the junction, then
The algebraic sum of the current that enter a junction equals zero, or 𝛴𝐼𝑖𝑛 = 0
To measure resistance is to use a circuit called a wheatstone brigde. The circuit illustrates a method of measurement know as the null method. In addition, to the unknown resistance R, a wheatstone bridge includes three otheer resistance 𝑅1𝑅2 𝑅𝑠
From the figure above, we get the equation:
𝑅𝑠 =𝑅𝐿𝐿1 2
= 𝑅𝑅1 𝑅2
(Raymond A. Serway.2004.1120) In a water pipe, the leght and cross-sectional area of pipe determine the resistance the pipe offen to the flow of water. Longer pipes with smaler sross-sectional areas offer greater resistance. Anologous effects are found in the electrical case. For a wide range of material, the resistance of a piece of material of length (L) and cross-sectional area (A) is 𝑅 =𝜌𝐿
𝐴
Where 𝜌 is a proportionality constant known as the “resistivity” of the material. The unit of 𝜌is Ωm. All the conductor are metal have small resistivities.
( John D, Cutnell and Kennent W. Johson.1989.522) The table of resistivities of various materials:
Mica 1011𝑥 1015
Teflon 1016
Iron 9,7 𝑥 10−8
(Paul M Fisbane.1996.710)
2. Design of the investigation
Measure the magnitude of resistance. Firts, tools and materials were prepared and were arranged.Second, resistor that has value 5.6 Ω as the 𝑅𝑥was arranged on the circuit on the right side.Then resistor that has value 2.7 Ω was arranged on the left side and then observe the move contact until the galvanometer is in zero or null current. Next long of 𝐿1 and 𝐿2 was writen. Step were repeated again but the resistor replace 3.3 Ω, 3.9 Ω, 6.8 Ω, 8.2 Ω.
So that, to measure the magnitude of copper wire resistivity. First, tools and materials were prepared and were arranged. Second, copper wire was arranged on the right side of circuit. Then, resistor that has value 2.7 Ω was arranged on the left side and then observed the move contact until the galvanometer is in zero or null current. Next, long of 𝐿1 and 𝐿2 was writen. Step were repeated again but the resistor is 3.3 Ω, 3.9 Ω, 6.8
Ω, 8.2 Ω. Measure the magnitude of nicel wire resistivity same as the step measure magnitude of copper wire, but the nicel wire replace witg copper wire.
3. Measurement techniques used
∆𝑅 𝑥 = 𝛴
(𝑅 − 𝑅𝑥 𝑥)2 𝑛 −1
b. Measure magnitude of copper wire and nicel wire resistivity 𝑅𝑘 = 𝑅𝑠𝐿1
Determine the magnitude of resistance
No 𝑅𝑠 (Ω) 𝐿1 (cm) 𝐿2 (cm) Determine the magnitude of copper wire resistivity
(𝑅𝑘 ±∆𝑅𝑘) = (3.10 ± 0.80)10−1Ω (𝜌𝑥±∆𝜌𝑠) = (8.78 ± 2.70)10−8Ω𝑚 Determine the magnitude of nicel wire resistivity
No 𝑅𝑠 (Ω) 𝐿1 (cm) 𝐿2 (cm)
1 2.7 80 20
2 3.3 84 16
3 3.9 87 13
4 6.8 89 11
5 8.2 93 7
Result :
Conclusion
1. Discussion and conclusion
The basic principle of the experiment was concept about resistance (R) was defined of the voltage (V) applied across a piece of masterial to the current (I) through the maerial.
For a wide range of material, the resistance of a piece of material of length (L) and cross-sectional area (A) is 𝑅 = 𝜌𝐴𝐿
To measure resistance was to use a circuit called a wheatstone brigde. In addition, to the unknown resistance R, a wheatstone bridge includes three otheer resistance 𝑅1 𝑅2 𝑅𝑠
𝑅𝑠 = 𝑅𝐿1 𝐿2
=𝑅𝑅1 𝑅2
The result of experiment wheatstone brigde were: Determine the magnitude of resistance
(𝑅𝑥±∆𝑅𝑠) = (5.21 ± 0.39)Ω
Determine the magnitude of copper wire resistivity (𝑅𝑘 ±∆𝑅𝑘) = (3.10 ± 0.80)10−1Ω
(𝜌𝑥±∆𝜌𝑠) = (8.78 ± 2.70)10−8Ω
Based the theory, the value of copper wire resistivity is 1.72 x 10 −8Ω . the value of copper wire resistivity based theory and experiment is different. Determine the magnitude of nicel wire resistivity
Based the theory, the value of copper wire resistivity is 1.72 x 10 −8Ω . the value of copper wire resistivity based theory and experiment is different. 2. Summary of conclusions
a. The magnitude of resistance b. (𝑅𝑥 ±∆𝑅𝑠) = (5.21 ± 0.39)Ω
c. The magnitude of copper wire resistivity a. (𝑅𝑘 ±∆𝑅𝑘) = (3.10 ± 0.80)10−1Ω b. (𝜌𝑥±∆𝜌𝑠) = (8.78 ± 2.70)10−8Ω𝑚 d. The magnitude of nicel wire resistivity
References
Cutnell, John D and Kennent W. Johnson.1989.Physics.Canada:John Willey and Sons Fisbane, Paul M.1996.Physics.USA:New Jersey Company
Fishbane, Gasiorowicz and Thornton.1996.Phisics.USA:Prentice Hall Serway, Raymond A.2004.Physics for Scientist and Engineering.California:
Thomson Brooks www.google.com/picture
