Question

A bar of iron is $10cm$ at ${20}^o$C. At ${19}^o$C it will be (${\alpha }_{Fe}$ = 11 x ${10}^{-6}{/}^{o}C$)

• A. $11x{10}^{-6}$ cm longer
• B. $11x{10}^{-6}$ cm shorter
• C. $11x{10}^{-5}$ cm shorter
• D. $11x{10}^{-5}$ cm longer

Answer 1

The correct option is C $11x{10}^{-5}$ cm shorter

generally when we are reducing the temperature of the iron bar it will become shorter than before

change in lenght$l_2=\alpha \left(l_1\right)(t_2-t_1)$

= $(11\times {10}^{-6})\left(10\right)(19-20)$

= $11\times {10}^{-6}\left(10\right)(-1)=11\times {10}^{-5}$ cm