Question

Explain the principle of a hydraulic machine. Name two devices that work on this principle.

Answer 1

(i) PRINCIPLE:-Consider two cylinders (A and B) having different areas of cross-section (a and b) fitted with watertight pistons and connected to each other through a pipe.

1. Let, Force applied at piston A = $F_1$
2. So, Pressure applied on piston A = $\frac{F_1}{a}$
3. Then according to the Pascal's law
4. Upward pressure exerted (transmitted) on piston B = $\frac{F_1}{a}$
5. Then,The upward force on piston B = Pressure x Area of cross-section =$\frac{F_1}{a}$$\times b$
6. Thus,

$F_2=$$\frac{F_1}{a}$$\times b$

and

$\frac{F_2}{F_1}=\frac{b}{a}$

When$b>a$ (i.e., cylinder B has a larger cross-section than cylinder A),

then

$F_2>F_1$

Thus, the force $\left(F_2\right)$exerted on the bigger piston is greater than the force $\left(F_1\right)$ applied on the smaller piston.

As a result, a small force applied on the smaller piston can easily lift a much heavier load on the larger piston.

Thus, a hydraulic machine acts as a force multiplier.

(ii) The two devices that work on this principle are as follows:-

1. Hydraulic press
2. Hydraulic jack
3. Hydraulic brakes