Question

What is a barometer? How will you construct a simple barometer?

Answer 1

A barometer is an instrument that is used to measure pressure.
We can create a simple mercury barometer by filling a long tube completely with mercury. We then fill a basin completely with mercury, and upturn the tube into the basin such that no liquid spills out. Then, we will notice the mercury level drop and reach a constant.
By measuring the height of mercury above the liquid surface, we can measure pressure as $P=\rho gh$
At atmospheric pressure, the mercury will rise to a height of $76cm$