Question: hi why does my hair stand up on end when I take of my hat on a cold or dry day

Kate Salmon answered on 17 Mar 2014:

Hi @pop112. This is a good question and you’ve done well to notice that it happens especially on dry days. First of all, let’s deal with the hat-hair bit. Rubbing certain materials together can cause the buildup of electrical charges on the surfaces. Opposite charges attract and same charges repel. When you take your hat off your head, you are rubbing your hat against your hair. This causes some of the electrons (negatively charged particles) to move from your hair to your hat and this loss of negative charge makes all of your hair ‘positive’. Same charges repel so all your hair will stand on end because they are all trying to repel each other and the farthest they can get is to stand up and away from all the other hairs.

This happens more on cold or dry days there is not a lot of moisture in the air. Moisture/water normally collects on materials when the air is humid and this can prevent the buildup of electrical charges. So on dry days when there is little water in the air, the charges can build up more and this is why you notice it more.