Question

______ metal is used in the bulb of thermometer.

Answer 1

Hint: Thermometer is used to measure the temperature of the body. So the substance used in the thermometer must have a high coefficient of thermal expansion. It should be sensitive to small temperature change . The metals satisfying these conditions should be the one which is used in a bulb or thermometer. In addition to this metals used in thermometers do not stick to the inner surface of the glass.

Complete answer:
We know that a thermometer is a material used to measure the temperature that is the degree of hotness or coldness of the body. So it should satisfy some conditions such as:
- It should have high coefficient of thermal expansion
- It should be sensitive to small temperature change
- Substance used must be in liquid form.
The thermometer consists of a bulb at one end followed by a long strip on which the readings are marked. It consists of a long glass tube which is graduated. Mercury is a metal which exists in liquid form at room temperature . It is a shiny liquid metal with a high coefficient of expansion. It also has a high boiling point which is suitable for measurement of higher temperatures.

Therefore, mercury is the metal used in the bulb of the thermometer.

Note:
The following points are essential for a substance to be present in the bulb of the thermometer:
i) It should have a high boiling point
ii) It should not observe a large amount of heat from the body that is being measured.
iii) It should show large changes for small changes in temperature.