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Young's Modulus Experiment

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⚡ Quick Summary
Experiment to determine Young's modulus of a wire by measuring the extension of the wire under different loads. The slope of the extension versus load curve is used to calculate Young's modulus.
['Stress = Mg / (πr²)', 'Strain = l / L', 'Y = (MgL) / (πr²l) = (MgL) / (πr²tanθ)']
Experimental Setup: A wire is suspended with a hanger at the lower end for adding weights. A vernier scale is used to measure the extension of the wire. Procedure:
  1. Measure the radius (r) of the wire at several places using a screw gauge.
  2. Determine the breaking weight using the standard breaking stress for the material and calculate the permissible weight (half of the breaking weight).
  3. Apply an initial load to straighten the wire and note the initial reading on the main scale and vernier scale.
  4. Add known weights gradually and note the extension after each addition, allowing time for full elongation.
  5. Repeat the experiment in reverse order, decreasing the weight and noting the extension at each step.
  6. Plot the extension versus load curve, which should be a straight line through the origin.
Calculations:
  • The slope of the extension versus load curve is tanθ = l / Mg.
  • Stress = Mg / (πr²)
  • Strain = l / L
  • Young's Modulus (Y) = (MgL) / (πr²l) = (MgL) / (πr²tanθ)