2B30.27 - Differential Pressure
To show differential pressure using a device called the Harbottle.
get the differential pressure glass piece and attach a balloon to the stem. push the balloon inside the glass. get a rubber stopper which fits the other side of the glass bulb. Grab a beaker for water. Include an anti-roll base for the glass bulb, so it does not roll off of the table by accident.
Blow the balloon up inside the glass bulb and place the stopper in the hole. The balloon will stay inflated inside of the bulb as long as the cork is in the hole of the tube because of the applied absence of atmospheric pressure between the bottle and balloon. When the hole is unplugged, air rushes into the hole to equilibrate the pressure. This pressure increase forces air out of the balloon and the balloon deflates. If you place water inside of the blown up balloon, prior to removing the cork, the rush of air into the bottle after the cork is removed is enough to expell the water out of the opening in the balloon.
When the pressure inside the balloon is equal to the pressure outside the balloon, it will not change size.