Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Mirrors would fog up if i didnt turn the fan on

  1. Sep 5, 2008 #1
    Hi guys,
    Recently i had noticed that when i left the hot water in the shower on for a while, the mirrors would fog up if i didnt turn the fan on, so what im wondering is how is it that the fan can prevent the windows from fogging up, im assuming the windows fog up because of water vapor but i'm not to sure.
  2. jcsd
  3. Sep 5, 2008 #2


    User Avatar
    Science Advisor
    Homework Helper

    Re: Water

    The mirrors fog up because they are below the temperature you have to cool water vapour to in order for it turn back into liquid water (called the dew point).
    This depends on the temperature and the relativity humidty - at higher humidity you don't have to cool as much in order to get water forming.
    The fan lowers the humidity by removing wet air and sucking in dry air from the rest of the house.
  4. Sep 6, 2008 #3
    Re: Water

    thanks mgb_phys
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook