Wheatstone Bridge new

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St. John's University *

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2280

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Mechanical Engineering

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Apr 3, 2024

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docx

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Wheatstone Bridge

No1 No2 No3 No4 No5 10 meters 10 meters 20 meters 20 meters 10 meters 22 Copper Wire 28 Copper Wire 22 Copper Wire 28 Copper Wire 22 Copper Nickel Wire Part 1: TABLE ONE: MEASUREMENTS / RESISTANCES WIRE NO. RUN # R 0 L 1 L 2= 100-L1 R X = L1/L2 x R0 Average: < R X > 5 1 20 39 100 – 39= 61 12.7 12.84 2 16 44.5 100 – 44.5= 55.5 12.82 3 12 52 100 – 52= 48 13 4 1 6 46.5 100 – 46.5= 53.5 5.21 4.34 2 5 47.5 100 – 47.5= 52.5 4.52 3 4 43.7 100 – 43.7= 52.7 3.31 3 1 1 51.1 100 – 51.1= 48.9 1.04 1.07 2 2 35.3 100 – 35.3= 64.7 1.09 3 3 27 100 – 27= 73 1.10 2 1 4 35 100 – 35= 65 2.15 2.13 2 3 42 100 – 42= 58 2.17 3 2 51 100 – 51= 49 2.08 1 1 3 27 100 – 27= 73 1.10 0.73 2 2 23 100 – 23= 77 0.59 3 1 34 100 – 34= 66 0.51 TABLE TWO: RESISTIVITIES WIRE NO. METAL LENGTH L DIAMETER D CROSS SECTION AREA A < R x > ρ 5 Copper-Nickel 10 m 0.635 mm 3.17 x 10^-7 m 12.84 4.07 x 10^-7 4 Copper 20 m 0.305 mm 7.31 x 10^-8 m 4.34 1.58 x 10^-8 3 Copper 20 m 0.635 mm 3.17 x 10^-7 m 1.07 1.69 x 10^-8 2 Copper 10 m 0.305 mm 7.31 x 10^-8 m 2.13 1.55 x 10^-8 1 Copper 10 m 0.635 mm 3.17 x 10^-7 m 0.73 2.31 x 10^-8 Average p = 1.78 x 10^-8 Discrepancy of Copper Wires: 3.48%

Questions: Question 1 . Is it possible that, during your experiment, the resistance of one of your wires has changed? If yes, what is the likely reason? What precautions should be taken to guard against this? A: There is a possibility that the resistance of the wire changed. In addition to human error during the experiment, the wires could have overheated or over cooled. As a result of this effect, there could be a change in area or length. In order to prevent the issue, we can use thicker wires which will minimize the resistance. Also, when not using the current, disconnect the wires from the power source to prevent overheating. Question 2 : In this experiment, there is an uncertainty of 0.1cm in locating the Balanced Bridge Position. What % error will this uncertainty cause in calculations of L 1 , of L 2 ,and of the ratio L 1 / L 2 , when L 1 happens to be (a) 20.0 cm (b) 90.0cm (c) 50.0 cm? Show the details of your calculations  and display the results in the table. A: QUESTION 2 BRIDGE BALANCE D AT % ERRORS IN L 1 L 2 L 1 L 2 L 1 = 20 cm 0.5% 0.125% 0.625% L 1 = 90 cm 0.11% 1.0% 1.11% L 1 = 50 cm 0.2% 0.2% 0.4% 

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Case 1: Case 2: Case 3: Question 3 : On the basis of the above table for Question 2, explain the reasons for the suggested values of R 0 in “Procedure”.

A: The reasons for the suggested values of R 0 in procedure is to help decrease the percent error. We need to know the suggested values of R0 from the procedure in order to have a low value for percent error. We can find that the closer we are to 50 cm the lower the percent error is. Conclusion: In the final analysis, we were able to learn how to calculate the resistivity of metals. We were able to comprehend how the Wheatstone Bridge is used to accumulate accurate measurements of resistance. Since the percent discrepancy was 3.48%, we can conclude that there was only a small amount of error when finding the values of the copper samples.