Question

If a bimetallic strip is heated. It will
A) Bend towards the metal with lower thermal expansion
B) Bend towards the metal with higher thermal expansion
C) Twist itself into a helix
D) Have no bending

Answer 1

Hint: The bimetallic strips have two different metals composed together. Those metals have different thermal expansion coefficients. Thus for the same temperature given to both, they react differently.

Complete step by step answer:
The bimetallic strips are commonly used in thermostats. It is because the temperature change will bring the mechanical displacement in the metal. They are also used in the appliances which are sensitive to even small temperature changes. Such as thermometers, clocks, and other electrical devices.
The strip of bimetal comprises two metals with different coefficients of thermal expansion. The metal with a higher coefficient will expand at first when heated. The expansion results in bending. Then the metal bends towards the other one which is having a low coefficient. The condition is reversed when the bimetal is cooled from its initial temperature.
When the temperature is decreased the metal low coefficient of thermal expansion will bend towards the other.
When the bimetallic strip is heated, the metal with higher thermal expansion will bend more. Thus they bend towards the metal having a lower thermal expansion.

Therefore, the correct answer is option A.

Note:
One of the examples of the bimetallic strip is brass and steel. The brass has a higher coefficient of thermal expansion. Thus when heated it will bend towards steel and when cooled the steel will bend towards brass.