Question

Which of the following works on Pascal’s law?
a) Sprayer
b) Venturimeter
c) Hydraulic lift
d) Aneroid Barometer

Answer 1

Pascal’s law deals with pressure and areas. Keeping this in mind, look for a device which depends largely on area.

Complete answer:
Pascal’s law states that pressure applied on a confined liquid is distributed or transmitted evenly throughout the liquid. Pascal’s law is mathematically expressed.
$F = P \times A$ where,
$F$ is the force applied.
$P$ is the pressure transmitted
$A$ is the cross sectional area
We will one by one go through the working of devices mentioned. First of all we have Sprayer. The air flows at a high velocity through the tube when the Plunger is pushed in . a region of low pressure is created just above the tube due to the flow of air at high speed. Due to this the fluid leaves the tip of the tube through the nozzle as a fine spray which is carried by fast moving air. This behaviour is explained by Bernoulli’s principle. So this is not the correct option.
Moving on to Venturimeter is the most widely used device to measure the discharge through the pipe. A venture is the converging – diverging nozzle of a circular cross-section. Flow of liquid through it flows the continuity equation and is not related to pressure being exerted on it’s walls. So this option is also incorrect.
Now we have an Aneroid Barometer which is built around a sealed box that expands or contracts with increasing pressure. As it moves, it pulls or pushes a spring and a system of levers, moving a pointer up or down the dial. So it is a simple device with no practical application of Pascal’s law.
Next we have Hydraulic Lift. It allows us to use a relatively small input force to create a larger output force. This occurs because the pressure that is applied on one piston is equal to the pressure that the second experiences. This is the principle of Pascal’s law.

So, option c is correct.

Note: Deep conceptual knowledge of working of devices related to Pascal’s law i.e. flow or pressure of liquids is required. One should have a good understanding of laws governing their working.