Consider a bimetallic strip consisting of a 0.50-mm- thick brass upper strip welded to a 0.50-mm-thick steel lower strip.When the temperature of the bimetallic strip is increased by 20. K, the unattached tip deflects by 3.0 mm from its original straight position, as shown in the figure. What is the length of the strip at its original position?

THINK:
The linear expansion coefficient of steel is 
The linear expansion coefficient of brass is 
So the brass will become larger in length.
SKETCH:
The figure is as below:
RESEARCH:
From the diagram,
…… (1)
Relation between arc length
, angle
and radius
is given by
, so
…… (2)
…… (3)
The new lengths of the strips after increasing temperature are given by
The increased length of the each strip is
…… (4)
…… (5)
Here the initial lengths of the both are same 
SIMPLIFY:
From equation (2), (3)
…… (6)
Substitute the equations (4) and (5) in the equation (6), we get
…… (7)
Here 
From the equation (1), 
Now consider the difference,

From the equation (2) and (3), we get
Therefore,
…… (8)
From the equation (7) and equation (8), we get
…… (9)
CALCULATE:
Given,
Thickness of the each strip is 
Temperature increased is 
The unattached tip deflects by 

Calculate the value of
:

By substituting all known values in the equation (9), we get
