Question

Two metal strips that constitute a bimetallic strip must necessarily differ in their:
(A) Length
(B) Mass
(C) Coefficient of linear expansion
(D) resistivity

Answer 1

Hint: A bimetallic strip is made so that when there is an increase in temperature the constituent metals expand differently. An application is as a current dependent key to cut off circuit by bending away from the circuit so it leaves it open.

Complete Step-by-Step solution:
Generally, a bimetallic strip is simply a strip of two different metals (i.e. of different elements or alloy, etc) combined together. Often bimetallic strips are made so that an increase in temperature of the metals will cause them to expand differently. This tends to leave the metal bent (like in a C shape or so). The different metals are expanding differently because they have different coefficients of linear expansion.
The bimetallic strip has some applications (which may help you remember how it works), such as use as a current dependent switch or fuse. In this case, the bimetallic strip is used as a key to complete a circuit. However when the current is increased to a certain amount, the temperature of the metals increase enough to allow the strip to bend away from the circuit, hence opening the circuit.

The correct option is C.

Note: For clarity, This is because as the metals expand differently, the length of one tends to be longer than the other, but since they are tied to each other, the longer one bends to allow itself in the direction of the shorter one (the one with the lower linear expansion coefficient) to expand to the required length (according to the temperature). When it bends, it gives it the opportunity to be longer without going further out.