Why do dry rooms have more static? This is because water in the air naturally conducts electricity.
What is static electricity? Every atom has positively charged protons, negatively charged electrons, and neutral neutrons. Almost all atoms have an equal number of protons and electrons, making them stable and electrically neutral. If an atom picks up electrons, it wants to lose them again, so it can go back to being stable. If an atom loses electrons it wants to get more so it can also go back to being stable. As we go about our daily life, the atoms in our skin can pick up extra electrons from our clothes, or the things we touch. These electrons stick to our atoms, but the atoms don’t want them. A buildup of electrons is the way that any electrical circuit works. Something produces picks up electrons and wants to lose them again. The negative electrons are attracted to negative protons, so a circuit uses this to get the electrons to move to the protons, which creates electricity. This is the same reason that we get lightning storms. The ice and water molecules in the storm strike each other, building up an imbalance of electrons, which discharge to parts of the ground that are close enough.
If you walk across a synthetic carpet, or wear polyester clothes, the electrons are only loosely bound to the atoms and can be attracted to you very easily. When you touch something that is a good conductor, such as a metal door handle, the extra electrons will jump from you to the conductor. If you have picked up enough electrons, you may see the spark and feel pain. The electrons rush to the protons in the metal door handle and stimulate the pain receptors in your skin as they pass, which is why they hurt. If the electrons were allowed to leave your hand slowly, it wouldn’t hurt.
Static electricity is also responsible for your hair standing up and for things sticking to you. When you take off a hat or rub a balloon on your hair, electrons stick to your hair. These electrons are all negatively charged and negative charges repel negative charges so your hair stands up. It is not the hair that is moving, but the electrons trying to get away from each other. It is also why things like paper stick to you. If you have picked up electrons and you are negatively charged, when you touch a piece of paper, the electrons in your hand repel the electrons in the paper and they move to the far side, while the protons are attracted to your hand. This movement gives the piece of paper a low positive charge and it is attracted to the negative charge in your hand, meaning you can’t put it down.
As an interesting aside, static electricity on the level we have it today is a relatively modern problem. Wall to wall carpets only became popular after World War 2, when more people could afford them. Before that, most floors were wooden or linoleum. Synthetic fibers were also invented after World War 2. Obviously, static electricity existed because it is a property of any atom, but our modern living has probably worsened it.
So, why do dry rooms have more static? It is to do with the properties of water molecules. Water is an excellent conductor of electricity. If the humidity in the room is above 40 percent, the electrons in the air, or the electrons that build up on your skin will be conducted to the ground. Static can still build up, but it is less likely. If the humidity is over 55 percent, static electricity is impossible because the electrons are conducted away before they have any chance to build up. When the humidity is low, such as in the winter or when the heater is on high, the electrons don’t get conducted away and can build up easily. If you are having a problem with static electricity, one solution is to get a humidifier.
So, water in the air conducts the extra electrons that build up on things to the ground, preventing them from building up on you, which is why a humid room has less static. And this is what I learned today.
Sources
https://en.wikipedia.org/wiki/Static_electricity
https://www.loc.gov/everyday-mysteries/physics/item/how-does-static-electricity-work/
https://www.condair.com/humidifiernews/blog-overview/why-does-low-humidity-cause-static-electricity
https://www.actionnews5.com/2018/12/19/breakdown-why-theres-so-much-static-winter/
https://aristair.com/blog/what-you-dont-know-about-static-is-shocking-consider-humidification
https://justenergy.com/blog/electric-shock-what-how-and-why-dangerous/
https://www.baypower.com/blog/is-lightning-static-electricity/
https://www.msichicago.org/science-at-home/hands-on-science/static-cling/