Question

Coefficients of linear expansions of two metals are in the ratio 3:4. The ratio of initial lengths of rods so that the expansions may be equal when heated through the same range of temperature is

• A. 3:4
• B. 4:3
• C. 1:1
• D. 4:1

Answer 1

The correct option is B 4:3

Expansion = $l\alpha \Delta T$
Since for same $\Delta T$, it is given that the expansions are same, so we get
$l_1{\alpha }_1$ = $l_2{\alpha }_2$
So, $\frac{l_1}{l_2}=\frac{{\alpha }_2}{{\alpha }_1}=\frac{4}{3}$