Question

The moisture present in the mercury ___________ the barometric height of a simple barometer.
A. increases
B. decreases
C. doesn’t change
D. can’t say

Answer 1

Hint: The instrument that measures air pressure is a barometer. Pressure tendency can forecast short term changes in the weather.

Complete step by step solution:
Barometer is a device used to measure atmospheric pressure. There are two types of barometers, mercury and aneroid. In the mercury barometer, atmospheric pressure balances a column of mercury, the height of which can be precisely measured. A non liquid barometer called the aneroid barometer is used in portable instruments and in aircraft altimeters because of its smaller size. It contains a flexible-walled evacuated capsule, the wall of which deflects with changes in atmospheric pressure. This deflection is coupled mechanically to an indicating needle. A mercury barometer is used to calibrate and check aneroid barometers. When atmospheric pressure rises, the mercury column in a barometer rises and when atmospheric pressure falls, the height of mercury in the barometer falls. If there is moisture present in mercury, its density and vapor pressure will increase and so the barometric height increases.

Hence, the correct option is (A).

Note: In 1643,Toricelli invented the mercury barometer when he inserted a glass tube in a dish of mercury and observed the day-to-day variations in the height of the mercury column.He noticed that mercury descended to a height of about and stopped. He also noticed that even if the thickness or slope of the glass tube changes, the height of the mercury column does not change. This is because the pressure is equal to the air pressure acting on the surface of the mercury and the mercury column in the glass tube.