Question

A matal rod is heated till its length becomes twice of its original length. If coefficient of linear expansion of the material of the rod is infinity , then what is the change in temperature?

Answer 1

Linear expansion:△L=α L △tGiven that △L and △t are constants.Hence,α L=constantL1L2=α2α1        =4:3

Answer 2

Supposed at normal temperature T the length of the rod is L.When the rod is heated at temperature T` its length becomes 2L ( according to questions and using point 1. Assumption )The coefficient of linear expansion = alfa

Now from linear expansion, we know

Alfa = change in length/ length× change in temperature

i.e. alfa = 2L-L/ L×( T`-T)

Or (T`-T) × L = L /Alfa

Or (T`-T) = 1/ Alfa

The change in temperature will be inverse of it's given the coefficient of linear expansion.