What do you mean by Bimetallic strip thermometer?

Hint:Here, you are asked what is a bimetallic strip thermometer. As the name is bimetallic strip thermometer, it is a thermometer. So, it is a device which is used to measure the temperature of a system, the degree of hotness or coldness of that object. You are not asked whether it is a thermometer or not, you are asked to find out what kind of thermometer it is, what are the main components of the thermometer, on what principle does it work and how it works. You need to include all these mentioned things in your answer. Also, to proceed, it is something related to the thermal expansion of an object.

Complete answer:
When an object is heated, that is, when the temperature of the object is increased, it tends to expand. The expansion of the object can be length expansion, surface area expansion or volume expansion. There is a term called the coefficient of thermal expansion which gives you the description of how the size of an object changes with temperature.

This coefficient of thermal expansion is specific. Metals and alloys have their own coefficient of expansion. This means that for the same increase in temperature, the change in size of each substance will be different. So now, let us come back to our question, what is a bimetallic strip thermometer?

As the name suggests, bimetallic strip, we join or couple two strips of different metals. Now, if the temperature of the bimetallic strip is changed, there will be expansion that will occur. As said, both are different metals, so obviously the change in the size or expansion in them will be different due to different coefficients of expansion.

As they are coupled together, they cannot increase their length by the same amount and eventually, the bimetallic strip bends. This deformation is caused due to change in temperature and can be measured in scale of temperature. As you can see that it can be used in order to measure temperature.

Therefore, a bimetallic strip thermometer is a coupled strip which bends due to change in temperature.

Note: We have told you that when the temperature is increased, an object tends to expand. The thing to be noticed here is that when the temperature of an object is decreased, it is contracted. So, if we have discussed only the expansion part, that does not mean that contraction does not happen, it happens. So, keep this in mind. Also, remember the coefficient of expansion describes the expansion of an object with change in temperature.