Physics
Static electricity
Crackling sweaters, sticking balloons and lightning in the sky: all the same physics.
What you need first
You rub a balloon on your hair, hold it against the wall, and it sticks. When you pull off your sweater it crackles, and in the dark you can even see tiny sparks. What happens there is the same physics as a lightning bolt in a thunderstorm, just much, much smaller. The key lies in the smallest building blocks of matter: atoms.
Charge is inside every atom
Every atom has a nucleus with positively charged , and negatively charged electrons whizzing around the outside. The nucleus also holds neutrons, which carry no charge at all and therefore play no part in static electricity. Normally there are exactly as many protons as electrons, so plus and minus cancel out and the atom is neutral to the outside. The important part: the protons sit firmly in the nucleus, but the outer electrons are fairly loose. You can literally rub them off.
The proton count determines the element, the electrons determine the charge.
Rubbing moves electrons
When you rub the balloon on your hair, electrons travel from your hair onto the balloon. The balloon now has a surplus of electrons and is negatively charged. Your hair is missing electrons, so it is positively charged. And now the most important rule of electricity applies: like charges repel, opposite charges attract. That is why your hairs stand up one by one, because each positive hair pushes its positive neighbours away. And that is why the negative balloon attracts your positive hair. It even sticks to a wall, although the wall is neutral: the negative balloon pushes the electrons in the wall's surface a little deeper in, so the surface right there turns slightly positive and holds the balloon.
Sparks and lightning
Charges want to balance out again. If the difference gets big enough, the electrons simply jump through the air: that is the little spark that crackles when you pull off your sweater or zaps you at the door handle. Lightning is exactly the same thing, only huge: inside a storm cloud, ice grains and water droplets rubbing against each other charge up large regions until the tension discharges in one enormous spark, often between two parts of a cloud, sometimes between cloud and ground.
Exercises
0 of 6 solvedTime to try it yourself. You can't break anything, every attempt counts.
Which particles move from one material to the other when rubbing?
Two negatively charged balloons hang next to each other. What happens?
An atom has 6 protons and 6 electrons. What is its total charge?
You rub a balloon on your hair. Electrons move from the hair onto the balloon, so the balloon becomes … charged.
A particle has 8 protons and 10 electrons. What is its charge? (Include the sign)
Match each charge state to what it says about the body.
Where this leads