Measuring Young modulus of copper

Data Analysis and Results

1. Measurements of the diameter of wire

Mean diameter of wire d = 0.0003m

2. Measurements of the original length of wire

3. Measurements of the extension of the wire with load and hanger(0.0996kg)

4. Graphs of load against extension

-1st measurement (failure)

-2nd measurement*

-3rd measurement*

 * The red points are the centroids of slope of straight line 

  %strain = (extension/original length) x 100%

6. Measurement of slope of the graphs

Slope of graph = load/extension

7. Young’s modulus of copper calculation

E = slope of graph x (4gl/πd2)    where g=10ms-1

Error Estimate

1. Calculation of error of slope

2. Calculation of error of length and diameter of the wire

3. Estimation of the percentage error in E

% error in E = % error in slope + % error in l + 2 x % error in d

Discussion

1. Precautions

2. Errors

Conclusion

The 1st measurement is failure because the length of the wire is measured after the hanger is loaded at the end of the wire. Therefore, the experiment result is not accurate because the length of the wire is included the extension with the hanger.

The 2nd and 3rd measurements are proved that copper wire obeys Young modulus and Hooke’s law in elastic deformation condition. The stress (or the load) of the wire was directly proportional to the strain (or the extension) of the wire in elastic deformation. The deformation is remained elastic when the wire is loaded 0.8kg (elastic limit) of slotted masses in the graph shown. The yield point was the wire which is loaded 0.9kg slotted masses. The breaking stress of the copper wire was 1.4kg in both measurements.