The ends of the two rods shown in the figure are separated by 5.0 mm at 25 °C. The left-hand rod is brass and 1.0 m long; the right-hand rod is steel and 1 m long. Assuming that the outside ends of both rods rest firmly against rigid supports, at what temperature will the ends of the rods that face each other just touch?

THINK:
The coefficient of linear expansion depends on the temperature and initial length.
Linear expansion coefficient for brass is 
Linear expansion coefficient for aluminum is 
RESEARCH:
The change of length
with change in temperature
is given by
…… (1)
Here
is the linear expansion coefficient,
is initial length.
CALCULATE:
Given,
The length of the brass rod is 
Length of the steel rod is 
Separation between two rods is 

Initial temperature is 
Let the final temperature is 
Change in temperature is 
The change in the length of brass rod is

The change in the length of steel rod is

To fill the gap the total linear expansion of given two cubes is must equal to the gap between them.

Therefore the required temperature will the ends of the rods that face each other just touch is
