The weights will be added in 100-gram increments, and then the marker at the wooden blocks will show if there is any slip, (It will be on top of a scale and if it’s moved from there slip has occurred). Then, the extension (minus any slip) will be obtained and tabulated. This will be done by measuring the length of the wire from between the two markers, and then measuring the extension of the wire from the second marker. The weights will be added in 100 grams because this provides enough results without going in to small increments.
The variable in this experiment will be the constant increment of force added to the wire.
The expected force that the wire can support (based on preliminary work) will be up to and around 12 Newton’s’ which is when fracture occurred.
Measurements to be taken
The measurements to be taken at the start of the experiment will be the diameter of the wire (to calculate it’s cross sectional area), the original length of the wire without force added, the distanced from both markers to the ends (wooden blocks and the roller pulley).
The measurements to be taken during the experiment are the length of the extension (a scale will be laid parallel to the vertical wire), which will take into accounts any slip that occurs. To check if any slip is occurring then the distances of the wire from the markers to the ends will be taken and then checked against the original distance. This will be checked after every subsequent weight is added, and noted, to an accuracy of half a millimetre.
Other measurements made will be the accuracy of the apparatus, such as the micrometer screw gauge must be zeroed before measuring the diameter, and the accuracy of the weights. Percentage error will be calculated in the evaluation.
Safety Points
The experiment is a safe experiment, but there is a chance of the weights dropping onto the experimenter’s foot, which can be avoided easily. The wire after fracturing may lash out to the other side of the bench. This can be avoided by not adding the weights if and when there are persons on the wooden block side of the wire.
Apparatus
- Wire (around 3.5 meters)
- 2x wooden blocks
- 1 G-clamp
- Weight Hook
- 12-15 weights. (100g each)
- Accuracy – 0.1g in 100g = 0.1% error
- Roller Pulley
- Celotape
- Micrometer Screw-gauge.
- Accuracy – 0.01mm in 0.19mm = 5.36% error
- Scale (e.g. Rule)
- Accuracy – 2mm in 3570 mm = 0.06% error
Total Approximate error range: 5.52% = 6%
RESULTS:
Note: I have taken the force of one Newton to be the where the extension because I found it difficult to measure the length of the wire without pulling on it. This was because the wire was coiled originally and so kept trying to go back to its original coiled state. This means my wire length will be inaccurate to approximately half a millimetre. This would not have affected the permanent length of the wire because the wire enters the plastic region only after around 10 Newton’s (Represented on a graph of axis force against extension)
The slip mentioned in the results refers to how much the wire has been pulled from the two markers, which is referred to in the method. The slip is evidently not part of the extension and will be taken into account.
Original Length of the Wire = 3570mm. = 3.57 meters
Original Diameter of the wire = 0.175mm = 1.75 x 10-4 meters.
Area = 0.0000000962m3 = 6.92 x 10-8m3
These results may be unduly accurate and this will be taken into account in the conclusion. As the Young’s Modulus concerns the region where Hookes Law is obeyed, then this will be the region where the extension increases in small equal amounts. In this case it is 1-9 Newton’s here. As this only caused small extensions of 1mm per each weight added, this is where the biggest errors will occur.
Ruler to half millimetre accuracy
0.5mm in 8mm = 0.5 / 8 * 100 = 6.25%
CONCLUSION
What is Young’s Modulus Of Elasticity for Nicrome Wire?
Young’s Modulus For Elasticity is defined as Stress Over Strain.
So (Force * Length) * (Extension * Cross-sectional Area)
This is the gradient of a graph representing stress over strain. (In the region where Hooke’s Law is obeyed)
Stress-Strain Graph:
Gradient:
Δy = (8 x 107 – 2.7 x 107) = 53000000 = 5.52 x 1011 GPa
Δx = (1.88 x 10-3 – 9.2 x 10-4) = 0.00096
The gradient of the graph represent the stress over the strain. The gradient over the Δy/Δx region is big enough to provide a good average. It is more accurate than the tabulated result because it contains the linear y=mx+c graph (This is due to Hook’s Law) which is the line of best fit for the results (The average)
The y-intercept on the graph is very close to the origin, which is what would be expected because if there were no stress (e.g. no force acting on the wire) then there would be, by definition, no strain, as there would be no extension occurring.
This shows that this area is obeying Hook’s Law because using the y=mx+c equation, this would say c ≈ 0 (approximately equal to 0). So y=mx where ‘t’is the stress, ‘x’ is the strain, and ‘m’ is the constant; being Young’s Modulus.
Conclusion:
My results are accurate, because the graph was a very straight line, as all the points could be plotted to a good degree of accuracy to the original plot from the y=mx equation;
Stress = (5.52 x 1011 ) x Strain
:-> Where 5.52 x 1011 Gpa is my result for Young’s Modulus for Nichrome Wire
Dividing the result of multiplying the stress by my Young’s Modulus by the original, and multiplying by 100 calculated the error from original column.
For every multiplication I got a a result of 6.72%, which is close to my approximate error range of 6%.
My results compared to my prediction:
My results, did not entirely agree with my prediction. From preliminary experiments the Young’s Modulus would be in the region of 180 GPa. Also, from sources the modulus of elasticity for nickel is