P2aL13 Static Electricity

Key Words

Atoms  - smallest particle of an element, consisting of protons, neutrons, and electrons

Attract - pull towards.

Electrical insulators - materials that do not allow electricity to flow.

Electrically charged particles - particles that have gained a positive or negative charge.

Electrons - tiny particles that carry negative charge which orbit the nucleus.

Negative electric charge - occurs in a particle having more electrons than protons.

Neutral charge - the number of electrons in a particle is balanced by exactly the same number of protons.

Positive electric charge - occurs in a particle having fewer electrons than protons.

Protons - positively charged particles found in the nucleus of an atom.

Repel - push apart.

Grade E

Static electricity occurs when charges on insulating materials are separated.  Examples include:

• When you comb your hair on a frosty morning, your hair is attracted to the comb (OK, you use gel);
• Bits of paper are attracted to a ruler you have rubbed with a cloth;
• Your clothes crackle when you take them off;
• You get a small shock after walking on a nylon carpet.

Objects become electrically charged due to the movement of electrons, which are tiny particles that orbit around the nuclei of atoms:

• Negatively charged objects have an excess of electrons;
• Positively charged objects have too few electrons.
• Neutral objects have zero charge.  The electrons are balanced by the protons.

It's only electrons that move.  Protons NEVER move.

Grade C

If we rub a polythene rod with a cloth, we rub electrons from the cloth onto the rod:

The electrons move off the cloth onto the rod.  The rod becomes negatively charged, and the cloth gets positively charged.

If we rub an acetate rod with a cloth, the rod becomes positively charged.

The electrons are rubbed off the rod onto the cloth.  The cloth gains a negative charge, while the rod gets a positive charge, as the protons are left behind.  Remember that protons NEVER move.

Why polythene becomes negative and acetate positive is complicated.  Just accept that they do.

You have probably done a simple experiment where:

• You bring a charged polythene rod up to a freely hanging charged polythene rod.  They repel.
• You bring a charged acetate rod up to a freely hanging charged acetate rod.  They repel.
• You bring a charged polythene rod up to a freely hanging charged acetate rod.  They attract.

This tells us that:

Like charges repel; unlike charges attract,

On damp days, static electricity experiments don't work very well, because the charge tends to leak away with the humid atmosphere.

Grade A

The early Greeks knew about static electricity since amber, when polished, attracted dust.  This rather defeated the object of polishing it. 

Early physicists played around with static electricity generating machines to make sparks.  They tried to store the charge and got thunderclap shocks in doing so.  No Health & Safety in those days.  The Leyden jar was an early day capacitor.

Benjamin Franklin made his name by flying a kite into a thunderstorm.  Isn't ignorance bliss?