The Young modulus Flashcards – AQA A-level Physics (7408)

How should a wire be prepared and measured before a Young modulus experiment?

Secure a long, straight wire. Measure its original length $L$ and its diameter $d$ with a micrometer.

How is the original cross-sectional area of a wire calculated from its diameter $d$?

$A = \frac{\pi d^2}{4}$

How are extension measurements obtained for different loads in a wire experiment?

Add known masses and measure the extension for each load using a fixed reference scale.

What is the tensile force on a wire supporting a load of mass $m$?

$F = mg$

How is tensile stress calculated from force $F$ and original cross-sectional area $A$?

$\text{stress} = \frac{F}{A}$

How is tensile strain calculated from extension $\Delta L$ and original length $L$?

$\text{strain} = \frac{\Delta L}{L}$

How can the Young modulus be obtained from a stress–strain graph?

It is the gradient of the straight-line region when stress is plotted against strain.

Why should loads remain within the elastic region when measuring a wire's Young modulus?

So the wire returns to its original length when unloaded.