Question

A fixed volume of iron is drawn into a wire of length $l$. The extension produced in this wire by a constant force $F$ is proportional to :

• A. $\frac{1}{l^2}$
• B. $\frac{1}{l}$
• C. $l^2$
• D. $l$

Answer 1

Answer: (C)

$l^2$

let the volume be $V$ and area $A$

$Y=\frac{Fl}{A\Delta l}$

$\Delta l=\frac{Fl}{YA}$

$V=A\times l$

$A=\frac{V}{l}$

$\Delta l=\frac{F{l}^2}{YV}$