Manometry - Pascal's law & Absolute Pressure, Gauge Pressure & Atmospheric Pressure

2. Manometry 1. Pascal’s law:- The intensity of fluid at any point in a stationary fluid is same in all directions. P_x= P_y= P_z

Pressure varies only with depth in stationary fluids, whereas if fluids is in motion pressure may vary in horizontal direction also. Fluid pressure is measured in force/area and it is expressed in Pascal (N/m2) or bar. 1 bar = 105 N/m2 1MPa = 10bar Barometer shows atmospheric pressure. 1kgf = 9.81 Newton. Pressure is a scalar quantity. 2. Absolute Pressure:- Pressure measured with reference to absolute zero. Absolute pressure cannot be negative. Absolute pressure = Gauge pressure + local atmospheric pressure

P gauge = ρgh Here, ρ= Density of fluid g = acceleration due to gravity h = height Gauge pressure can be positive, negative or zero. Atmospheric pressure varies with altitude, temperature and local conditions. At mean sea level atmospheric pressure is 1.01 × 105 Pascal or 1 bar or 10.3m/s. of height of water or 76cm height of mercury.