# Jolly's Bulb Apparatus Experiment

The Jolly's Bulb Apparatus Experiment Viva Questions

(i) State the unit of pressure in S.I.

Ans: Nm-2

(ii) What is one atmosphere?

Ans: It is the pressure exerted by a column of 76 cm of mercury at 0 °C.
P = hdg = 0.76 x 13.6 x 103 x 9.8 = 1.013 x 105 Nm-2

(iii) Why should the air enclosed in the bulb be dry?

Ans: The presence of water vapour alters the reading

(iv) State Charles law

Ans: The volume of a given mass of gas varies directly as its temperature in Kelvin scale when pressure is kept constant. The pressure of a given mass of gas varies directly as its temperature when volume is kept constant ie, V T and P T

(v) Why do you use a capillary tube to connect the bulb to the reservoir?

Ans: To ensure that most of the air enclosed is at the constant temperature of the bath

(vi) What is the boiling point of pure water at normal pressure in Kelvin scale?

Ans: 273 K

(vii) How do you define pressure coefficient of a gas?

Ans: It is defined as the ratio of the increase in pressure of the gas at constant volume per degree rise of temperature to its pressure at 0 °C

(viii) Is the pressure coefficient the same for all gases? If so what is its value?

Ans: Its value is same for all gases and is equal to 1/273

(ix) Aim of the Jolly's Bulb Apparatus Experiment?

Ans: To study the relation between pressure and temperature of a sample of air at constant volume

(x) Apparatus of the Jolly's Bulb Apparatus Experiment?

Ans: Jolly's bulb apparatus, water bath, thermometer, etc. The Jolly's bulb apparatus consists of a spherical glass bulb A connected to a narrow capillary tube bent twice at right angles. There is a fixed mark M made on this tube as shown in the figure. The free end of the tube is connected to a reservoir R of mercury by means of thick rubber tubing. The reservoir can be raised or lowered and can be fixed in any position. The readings of the mercury levels may be noted on a scale S.

(xi) Theory of the Jolly's Bulb Apparatus Experiment?

Ans: For a given mass of gas (air) at constant volume, the pressure P is directly proportional to its absolute temperature T.
i.e., P T or (P/ T) = a constant