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Pressure
Pressure is the normal force exerted by a system against unit area of the boundary surface.
where δA approaches zero.
The unit for pressure in SI is pascal, Pa
Two other units are widely used
| 1 bar = 105 Pa = 100 kPa = 0.1 MPa |
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and the standard atmosphere, where
1 atm = 101.325 kPa = 1.01325 bar = pressure exerted by a columan of 760 mm of Hg
Energy
Energy is the capacity to exert a force through a distance. In SI, the unit of energy is Newton-meter, N m or Joule, J.
Power
The rate of energy transfer or storage is called power. The unit of power is watt, W.
1 W = 1 J/s = 1 N m/s and 1 kW = 1000 W.
Apart from these, the following units are used for various parameters of interest
Frequency, Hertz = Hz = s-1
Electric current, Ampere = A
Electric charge, Coulomb, C = As
Electric potential, Volt = V = W/A
Magnetic flux, Weber, Wb = Vs
Magnetic flux density, Tesla, T = Wb/m2 |
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