Static Electricity

The tiny world inside everything

Everything around you — your hand, a balloon, the floor, the air — is made of incredibly tiny bits called atoms. Atoms are far too small to see, even with most microscopes.

Inside every atom there are even smaller bits that carry electric charge. There are two kinds of charge: positive (+) and negative (−). Most of the time, an object has the same amount of each, so they balance out and the object is neutral (not charged). But if we move some charges around, things get interesting.

Rubbing makes static

The tiny negative charges (called electrons) can sometimes be rubbed off one object and onto another. When you rub two things together, some of these charges hop across.

• The object that gains extra negative charges becomes negatively charged.
• The object that loses them is left positively charged.

This build-up of charge that stays in one place is called static electricity. "Static" means staying still — the charge sits on the object instead of flowing along like the electricity in wires.

A great example: rub a balloon on your hair or a woolly jumper. Charges move onto the balloon. Now the balloon is charged with static electricity, and it can do some surprising tricks.

Pull together, push apart

Charges follow one simple rule:

Opposite charges attract (pull together). Same charges repel (push apart).

• A positive and a negative charge → pull towards each other.
• Two positives, or two negatives → push away from each other.

This rule explains everything static electricity does. Rub two balloons and hold them near each other — they push apart, because they both have the same charge. But hold a charged balloon near your hair, and your hair lifts up to reach it, because they have opposite charges!

Why a balloon sticks to a wall

Here is a classic trick. Charge a balloon by rubbing it, then hold it against a wall and let go. It sticks! But the wall is not sticky and the balloon is not glue. So what is happening?

The charged balloon has lots of extra negative charge. When you bring it near the wall, it pushes the wall's negative charges slightly away and pulls the wall's positive charges slightly closer to the surface. Now the part of the wall nearest the balloon is a bit positive — opposite to the balloon. Opposite charges attract, so the balloon clings to the wall. Clever!

Sparks and lightning

Sometimes static charge builds up a lot. When it finally gets a chance to jump across a gap all at once, you get a spark — a tiny flash and a snap. You might feel this as a little shock when you touch a metal door handle after walking on a carpet.

Lightning is the same thing, but enormous! Inside a storm cloud, water drops and ice crash about and rub together, building up a huge amount of static charge. When the charge becomes great enough, it leaps all at once — between clouds, or down to the ground — as a giant spark we call lightning. The flash you see and the thunder you hear come from that massive jump of static electricity.

Try it yourself: bend water with static

This experiment is like magic, but it is pure science.

You will need: a plastic comb or an inflated balloon, your hair (clean and dry), and a tap.

1. Turn on a tap so a thin, steady, gentle trickle of water flows.
2. Charge the comb or balloon by rubbing it on your hair about 10 times.
3. Slowly bring the charged comb close to the falling water — but do not touch it.
4. Watch! The stream of water bends towards the comb.

The charged comb pulls on the opposite charges in the water, so the water leans towards it. Try a balloon and pieces of tissue paper too — the charged balloon will lift them up!

Stay safe: keep electrical items away from the tap, dry your hands when you finish, and remember static from a balloon is completely harmless.

What we learned

Everything is made of atoms that carry positive and negative charge. Rubbing moves tiny charges, building up static electricity. Opposite charges pull together and same charges push apart — that is why a balloon sticks to a wall and your hair stands up. When static jumps suddenly it makes a spark, and lightning is a giant spark in the sky.

Want to know how electricity flows in wires instead of staying still? Read Electricity Basics, and explore the different kinds of energy in Forms of Energy.