In: Physics
describe an experiment to find the pressure coefficient of a gas at constant volume and that it is the same for all gases
Determination of pressure coefficient : Jolly’s bulb method.
Description:
Consider a bulb (A) kept in a container and is attached to a doubly
bent glass tube. The other end of the tube is connected to a rubber
tube, and the rubber tube is connected to a reservoir. The
reservoir is attached to a retard stand and it is free to move on
the retard stand. A vertical scale is fixed behind the rubber tube
to measure the pressure.
Procedure:
Send dry air into the glass bulb several times and moisture should
be removed from the glass bulb. Now the glass bulb is filled with
dry air and the reservoir is partially filled with mercury. Ice
cubes are kept in the container, so that the glass bulb attains 00c
temperature and the gas is cooled. Now mark the mercury level on
the rubber tube. The level difference in the two limbs can be
measured by the vertical scale and is noted as h1. The atmospheric
pressure H can be measured by Fortin’s Barometer.
The pressure at this temperature is noted as
Now the ice cubes are replaced with water and the water is boiled
upto temperature T. Temperature can be measured by thermometer .
After some time the bulb atains the temperature as the water and
the volume of the gas increases. The mercury in the rubber tube
moves down. But we have to find the pressure at this temperature at
constant volume, for that we have to raise the reservoir till the
mercury in the left limb reached point M. Now fix the reservoir and
the level difference in the two limbs is measured by the vertical
scale.
The pressure at this temperature is noted as
Pressure co-efficient of the gas can be measured by
Result of the Experiment
Experimental
result gives the Pressure coefficient of air as 1/
273.16/0C.