Question

If air has a dry-bulb temperature of 2°C

and a wet-bulb temperature of -2°C,
what is the relative humidity?

(1) 11% (3) 36%

(2) 20% (4) 67%

yea i know it’s either number 3 or number 4 but i can’t figure it out

Answer 1

The relative humidity is 36%.

Step-by-step explanation:

Relative humidity is the measure of ratio of actual vapor density to saturated vapor density in a given system. So there are different ways to measure the relative humidity in the atmosphere. One of the common ways is to measure using Psychrometer. In this instrument, two different thermometers are used as measuring device. One of the thermometer measures the humidity in dry air and another in wet air. So the difference of the temperature of dry and wet air bulb will be related to determine the relative humidity percentage. The formula to determine the relative humidity using this method is as below.

`Relative humidity=((e_(w)-[N*(1+0.00115*T_(w)*(T_(d)-T_(w)))])*100)/(e_(d) )`

Also,

`e_(d)=6.112*e^{[((17.502*T_(d) ))/((240.97+T_(d) ))]}`

And,

`e_(w)=6.112*e^{[((17.502*T_(w) ))/((240.97+T_(w) ))]}`

Here e =2.718,
`T_(d)` and
`T_(w)` are the temperature at dry bulb and wet bulb temperatures, respectively.

So, the relative humidity after substituting the values of Td = 2 C and Tw = -2 C is 36%.