Sci I - Static Electricity

What happens when certain materials are rubbed together?

Both materials become charged, one positive and the other negative.

Do we fully understand why certain materials become positive or negative when rubbed?

No, the exact reason is still a mystery.

What is static cling?

When oppositely charged materials stick together after rubbing.

Why don’t socks made of the same material cling in the dryer?

Because items of the same material do not exchange charges.

Why do cotton and acrylic socks cling in the dryer?

Because rubbing different materials makes them oppositely charged.

What everyday example can cause static electricity buildup?

Walking through your home on a dry day with socks rubbing against the rug.

Why does excess charge on your body want to leave?

Because the charges repel each other and want to spread out.

What happens if you touch a metal doorknob when charged?

The charges move through the air into the metal, creating a short-lived electric circuit and causing a shock.

What device uses static electricity to create effects?

A Van de Graaff generator.

How does a Van de Graaff generator build up charge?

A conveyor belt rubs materials together at the bottom, bringing stray electrons to the top, where they gather on a metal sphere.

What happens if you touch the metal sphere of a Van de Graaff generator?

Electrons travel into you, making you negatively charged.

Why does your hair stand up when touching the charged sphere?

Because each strand of hair becomes negatively charged and they repel each other.

How much charge do you build up on a Van de Graaff generator?

A tiny fraction of a coulomb.

What force does even a tiny charge overcome in the Van de Graaff example?

The gravitational force of the entire Earth pulling your hair down.

What does the Van de Graaff generator example demonstrate about electric vs. gravitational force?

It shows that electric force is much stronger than gravitational force.