Question

The following figure shows a manometer containing a liquid of density p. The limb P of the manometer is connected to a vessel V and the limb Q is open to atmosphere. The difference in the levels of liquid in the two limbs of the manometer is h as shown in the diagram. The atmospheric pressure is P₀.

(i) What is the pressure on the liquid surface in the limb Q?

(ii) What is the pressure on the liquid surface in the limb P?

Answer 1

(i) The pressure on the liquid surface in the limb Q is equal to atmospheric pressure i.e P_0.

(ii) According to the manometer principle, the difference in atmospheric pressure in two limbs is equal to the difference in height of liquid in two limbs.

So pressure at P = pressure at Q + h × p × g.

P₀= PQ + h ×p × g.