Measuring the Young Modulus

Here is a simple experimental set up for finding the Young Modulus of a material.

• A piece of wire is held by a G-clamp, sent over a pulley with the smallest mass attached to it. This should keep it straight without extending it.
• Measure the length from the clamp to the pointer. This is the original length (unstretched).
• Use a micrometer to measure the diameter of the wire in several places. Use this to calculate the cross-sectional area of the wire.
• Add a mass to the loaded end of the wire.
• Record the extension by measuring how far the pointer has moved from its start position.
• Repeat for several masses but ensuring the elastic limit is not reached.
• Remove the masses, one at a time taking another set of reading of the extension.
• Calculate stress and strain for each mass.
• Plot a graph of stress against strain and calculate the gradient of the line which gives the Young Modulus.

Here is a more precise way of finding the Young Modulus but involves taking the same measurements of extension and force applied.

It is called Searle’s apparatus.