Create the main points from the document given below:

\lcs.le etc. so press e liquid ) rovidq of liquid PHYSICS-IC tl 11/(- and ukes Pressure at N = atmospheric pressure = P . Pa = pgh = pressure at M. Where p is the density of mercury and h is the height of the mercury column in the tube. In the experiment it is found that the mercury column in the barometer has a height of about 76 cm at sea level equivalent to one atmosphere (l atm). A common way of stating pressure is in terms of em or mm of mercury (Hg). A pressure equivalent of 1 mm is called a torr (after Ton-icelli). 1 torr = 133 Pa. The mm of H2 and t01T are used in medicine and physiology. In meteorology, a common unit is the bar and millibar. 1 bar = 105 Pa. 2.Sv2 Manometer Manometer is a device used to measure pressure of any gas contained in a closed vessel. It consists of a Utube having some liquid. One end of the tube is open to the atmosphere and the other end is connected to the vessel containing the gas as shown in figure. c 4 h PW 2.8 (b) The pressure of the enclosed gas = The pressure at A = pressure at B . Pressure of the gas = P = P =PO+ pgh In general, pressure of the enclosed gas is given by P = P pgh Where Po is the atmospheric pressure, 'h' is the difference in levels of the liquid in the two limbs and p is density of the liquid. + Ve sign is used when level of liquid in open limb is above the level of liquid at A and Ve sign is used when it is below the liquid level at A. The excess pressure PPO is called the gauge pressure. Hydraulic Machines Whenever external pressure is applied on any part of a fluid contained in a vessel, it is transmitted unidiminished and equally in all directions. This is the Pascal's law for transmission of fluid pressure and has many applications in daily life. Basing on Pascal's law, devices such as hydraulic lift and hydraulic brakes are designed. In these devices fluids are used for transmitting pressure. In a hydraulic lift as shown in Fig. 2.8(c) two pistons are separated by the space filled with a liquid. A piston of small cross section A1 is used to a force Fl directly on the liquid. The pressure is transmitted throughout the liquid to the f wunder attached with a larger piston of area results in an upward force of P x A2. 47