Question

Two rods, one of aluminium and other made of steel, having initial lengths `l_(1) and l_(2)` are connected together to form a single rod of length `(l_(1)+l_(2))`. The coefficient of linear expansions for aluminium and steel are `alpha_(a)` and `alpha_(s)` respectively. If length of each rod increases by same amount when their tempertures are raised by `t^(@)C`, then find the ratio `l_(1) (l_(1)+l_(2))`.
A. `(alpha_(s))/(alpha_(a))`
B. `(alpha_(a)).(alpha_(s))`
C. `(alpha_(s))/((alpha_(a)+alpha_(s)))`
D. `(alpha_(a))/((alpha_(a)+alpha_(s)))`

Answer 1

Correct Answer - C
Given `Deltal_(1) = Deltal_(2)`
or `l_(1) alpha_(a) t = l_(2)alpha_(s)t :. (l_(1))/(l_(2)) = (alpha_(s))/(alpha_(s))`
or `(l_(1))/(l_(1)+l_(2)) = (alpha_(s))/(alpha_(a)+alpha_(s))`