12‐3 How is relative humidity measured?
(Pages 282‐283)
Relative Humidity: amount of water in air compared
with the amount of water the air can hold at capacity
What three things cause relative humidity to
change?
‐precipitation
‐evaporation
‐temperature change (up if temp up, down if
temp down)
If saturated, at capacity, what is the relative
humidity?
100%
If air filled to 1/3 of capacity, relative humidity is..
Psychrometer: instrument used to find relative
humidity
How do you find relative humidity?
‐Dry‐bulb thermometer reading
‐Difference between dry and wet bulb
thermometer readings
‐Find where they match up to give percent
Psychrometer Worksheet
Use the psychrometer to find the relative humidity....
Dry: 10oC and Wet: 5oC
Dry:
Difference:
Percentage:
Humidity and Comfort
We sweat to cool down, yet why does it cool us
down?
Moisture evaporating
Which climate is more comfortable:
Hot, dry climate OR Cool, moist climate
1
In Figure 12‐11, what city is going to be most
comfortable?
City A
Most uncomfortable?
City B
What do you think an air conditioner does to the air
temperature and humidity in a room?
Decreases both
2