Question

Two metallic strips that constitute a bimetallic strip must necessarily differ in their:
A. Length
B. Mass
C. Coefficient of linear expansion
D. Resistivity

Answer 1

Bimetallic strip is a thin strip which is made up of two sub strips which are made of different metals. Usually these metals expand or contract by different amounts when the temperature of the total strip increases or decreases. When the same amount of temperature is given to both sub strips they react differently. Due to this expansion or contraction the strip bends. With the help of this information, find the answer to this given question.

Complete solution:
As we know, bimetallic strips are generally used to convert a temperature change into a mechanical displacement. Now, this bimetallic strip generally has two strips of two different metals which expand at different rates when these strips are heated. Further, these different expansions cause a force that bends the strip in one way when heated and also bends in the opposite direction when cooled below its initial temperature.

So, from above observation we can say that the length, mass and the resistivity of the given two metallic strips does not matter much as the coefficient of linear expansion of these bimetallic strips.

Therefore, the correct answer is option C i.e. the coefficient of linear expansion.

Note:
Here, we must remember that the metal with higher coefficient of linear expansion is on the outer side of the curve when the strip is heated while it is on the inner side of the curve when the strip is cooled. Bimetallic strips can be used in flat form as well as wrapped into a coil. Also, these bimetallic strips are mostly used in mechanical and electrical devices.