Question

What is the effect of rise in temperature on the density of mercury in a barometer and hence its reading?

Answer 1

A barometer is a device that is used to measure atmospheric pressure. This pressure is also known as barometric pressure. It is the pressure measured within the atmosphere of Earth. It works by balancing the weight of mercury in the glass tube against atmospheric pressure.

Complete step by step answer:
Step I:
When any surface is in contact with air, the pressure exerted on it by atmosphere is known as air or atmosphere pressure. The temperature is the measure of heat. The temperature is inversely proportional to the density. When the temperature increases then the density will decrease.
Step II:
Density is defined as the ratio of mass and volume. So when the density of a substance increases, its mass will also increase. Due to increase in mass, more volume will be occupied by the same object. Due to an increase in volume of mercury, the level of mercury in the thermometer will also increase.
Step III:
A barometer has two columns and a glass tube. One of the columns is open and the other is sealed close. One of the ends of the tube is filled with mercury and then inverted. The vacuum in the tube will not let the tube be completely empty. The pressure inside the tube is balanced by the atmospheric pressure outside.

Therefore, the reading then obtained by the barometer will also increase.

Note: It is to be noted that one of the columns has mercury and the other column measures the atmospheric pressure. When the atmospheric pressure increases, then it forces more mercury into the reservoir and hence the mercury level increases in the column.