Q.What is Young's modulus? Describe an experiment to find out Young's modulus of the material in the form of a long straight wire.

Step 1. Definition. Young's modulus $Y$ is the modulus of elasticity linked to a change in length of a solid such as a wire or rod. For a wire of original length $L$ and radius $r$, loaded with mass $M$ at its free end producing elongation $l$: longitudinal stress $= Mg/\pi r^2$, longitudinal strain $= l/L$, so $Y = \dfrac{MgL}{\pi r^2 l}$, with SI unit N/m².

Step 2. Experimental setup. Take a long, thin, uniform wire of the material to be tested and suspend it vertically from a rigid support (a wall bracket or stand), with a small pan attached at its lower free end to hold weights, plus a reference marker (or vernier arrangement) to measure the very small resulting elongations precisely.

Step 3. Preliminary measurements. Measure the wire's original length $L$ between the fixed support and the reference marker using a metre scale, and its radius $r$ at several points along its length using a screw gauge (then average), so that its cross-sectional area $A = \pi r^2$ is known accurately.

Step 4. Procedure. Starting with a small initial load (to keep the wire taut), record the reference-marker reading. Then add known masses $M$ to the pan in equal steps, recording the new marker reading after each addition to get the elongation $l$ for that load; repeat while gradually unloading to check for consistency. …

State the defining formula, then describe the standard suspended-wire loading experiment step by step ( …

Using a single load-and-elongation reading to compute Y directly, instead of using a series of loads and taking the slope of the load-elongation graph, which averages o …