Question

Dalton's law is given as:
1. E_L = C[e_s + e_a]
2. EL = C[ea - e_s]
3. EL = C[es - e_a]
4. EL = C[es + e_w]

Answer 1

Correct Answer - Option 3 : EL = C[es - e_a]

Explanation:

Evaporation:

• The process of transformation of liquid water into a gaseous form is called evaporation.

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Dalton's law:

• It gives the relationship between the rate of evaporation and the difference between the saturation vapour pressure and existing vapour pressure, by the following expression

E_L = C(e_s - e_a)

Where, E_L = Rate of evaporation (mm/day), C = Constant, e_s = Saturation vapour pressure in mm of mercury, e_a = Existing vapour pressure in mm of mercury

Dependency of the rate of evaporation on various factors:

• Increases with an increase in vapour pressure at the water surface and air above it.
• Increases with increases in Air and water temperature.
• Increases when wind speed is above critical Wind speed.
• Decrease with the increase in Atmospheric pressure.

Instrument name	Used for measuring
Psychrometer	Relative humidity
Anemometer	Wind velocity
Pluviometer	Rainfall depth
Lysimeter	Evapotranspiration
Atmometer	Evaporation
Phytometer	Transpiration
Hygrometer	Relative humidity