Consider the image given below. The column is filled with water. The ends of each column A and B have been blocked by a piston. If piston A is pressed, what do you think will happen to piston B?
Piston B is going to rise up. We have just applied Pascal’s law to our fluid column. So what is Pascal’s law?
According to this principle, the external static pressure applied on a confined liquid is distributed or transmitted evenly throughout the liquid in all directions. The static pressure acts at right angles to any surface in contact with the fluid. Pascal also found that the pressure at a point for a static fluid would be same across all planes passing through that point in that fluid.
Let us understand the working principle with the help of an example.
A pressure of 2000 Pa is transmitted throughout a liquid column due a force being applied on a piston. If the piston has an area of 0.1 m2, what is the force applied?
This can be calculated using the following relation.
F = PA,
F is the force applied
P is the pressure transmitted
A is the cross sectional area
P = 2000 Pa = N/m2
A = 0.1 m2
Substituting values, we arrive at F = 200 N
The image you saw at the beginning of this article is a simple line diagram of a hydraulic lift. This is the principle of working of hydraulic lift. It works based on the principle of equal pressure transmission throughout a fluid (Pascal’s Law).
The construction is such that a narrow cylinder (in this case A) is connected to a wider cylinder (in this case B). They are fitted with airtight pistons on either end. The inside of the cylinders are filled with an in compressible fluid.
Pressure applied at piston A is transmitted equally to piston B without diminishing, on use of an in compressible fluid. Piston B effectively serves as a platform to lift heavy objects like big machines or vehicles.
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