Question

The figure shows a model of perfume atomizer. When the bulb A is compressed, air flows through the narrow tube. Consequently, pressure at the position of the vertical tube reduces. The liquid (perfume) rises through the vertical tube and emerges through the end. If the excess pressure applied to the bulb in this process be ∆p, the minimum speed of air in the tube to lift the perfume is:

• A.
• B.
• C.
• D. None of these

Answer 1

Answer: (A)

Answer 2

Applying Bernoulli’s principle at 1 and 2, we obtain

P₁ + 1/2 ρ_a = P₂ + 1/2 p

putting, v₁ = 0 since the air is at rest inside the bulb,

P₁ = P₀ + ∆p, P₂ = P₀ – ρgh where ρ = density of liquid

(perfume)

ρ_a = density of air v₂ = minimum velocity of air to lift the

liquid through the height h = v (say)

p₀ = atmospheric pressure

We obtain,

v =