Question

How will you show that there is vacuum above the surface of the mercury in a barometer?

Answer 1

If drop of water or alcohol is introduced in the space above mercury column,then the barometric height drops,as liqiuid (water or alcohol) vaporises in the vacuum and exerts pressure on the surfaceof mercury,thereby forcing it to fall down...the name givem to the vacuum is torricellian vaccuum..


The barometer is made up of glass tube closed at one end and other end with open reservoir of mercury at the base.The weight of mercury creates a vacuum in top of tube known as Torriceilian vacuum.The mercury in the tube adjusts untill the weight of mercury column balances the atmospheric force exerted on the reservoir.There is no space to any air to enter.So when the mercury goes down, there will be only vacuum as there are no breakage in the glass tube.