What is the atmospheric pressure and how is it determined using Barometer?

Explanation

1. Atmospheric pressure can be calculated with the help of the height of mercury column.
2. The weight of the mercury column in the tube is equal to the force applied on it by the mercury in the bowl due to atmospheric pressure.
`therefore` Weight of mercury column (W)
`="Mass of mercury column"(m)xxg`
`="Volume"xx"density"xxg`
`="Cross sectional are of the tube"xx"height of the tube"xx"density"xxg`
`=Ahrhog`
Let `P_(@)` be the atmospheric pressure.
Force on the column due to atmospheric pressure `=P_(@)A`
`" Then "ahrhog=P_(@)ArArrP_(@)=hrhog`
`"Here"'rho'and'g'"are constants. So the height of mercury column depends on the atmoshpheric pressure."`
We know height of mercury column h `=76cm=76xx10^(-2)m`
Density of mercury `(rho)=13.6gm//"cc"=13.6xx10^(3)kg//m^(3)`
Acceleration due to gravity `(g)=9.8m//sec^(2)`
`P_(@)=hrhog=76xx10^(-2)xx13.6xx10^(3)xx9.8=1.01xx10^(5)kg//m^(2)s^(2)`
`1kgm\\sec^(2)=1"Newton"`
`P_(@)=1.01xx10^(5)N//m^(2)`
This value is called atmospheric pressure.
1 Atmosphere `=1.01xx10^(5)N//m^(2)=1.01xx10^(5)"Pascal"`