Static Electricity — Science Sage

What is static electricity?

Static electricity is a build-up of electric charge on the surface of a material. Unlike current electricity (which flows), static charges stay in one place — hence "static" (stationary).

Everything is made of atoms, which contain protons (+) and electrons (−). Normally these charges are balanced and an object is neutral. Static electricity occurs when electrons are transferred from one material to another.

Charging by friction

When two certain materials are rubbed together, electrons (not protons or neutrons — these don't move) transfer from one material to the other:

The material that gains electrons becomes negatively charged (−)
The material that loses electrons becomes positively charged (+)

Key rule: Only electrons are transferred during rubbing. Protons and neutrons are locked in the nucleus and cannot move between materials.

Examples: Rubbing a plastic/perspex ruler with wool or silk; rubbing a balloon against your hair; shuffling across a carpet in socks.

Attraction and repulsion

⊕ ⊖

Opposite charges ATTRACT

A positive object and a negative object pull towards each other.

⊕ ⊕

Like charges REPEL

Two positive or two negative objects push away from each other.

A charged ruler placed near small pieces of tissue paper will attract them — the charged ruler induces an opposite charge on the surface of the paper closest to it.

Discharge and sparks

When the build-up of charge becomes large enough, electrons jump across an air gap — this is a discharge. You see it as a spark and feel it as a shock. Static discharge is more common when the air is dry (humid air allows charges to leak away more easily).

Lightning is a massive static discharge. Moving air and water particles in a storm cloud rub against each other, transferring electrons. The cloud becomes charged, and when the charge is large enough, a giant spark (lightning bolt) discharges between the cloud and the ground.

Safety during lightning storms

Stay indoors or inside a car (the metal shell conducts charge safely around you)
Avoid tall trees, open fields, hilltops, and water
Do not hold metal objects outdoors
Lightning conductors on buildings provide a safe path for charge to reach the ground

Links forward: Static electricity connects to the electric force (electrostatic force) covered in Grade 9 Forces. The charges created here are the same phenomenon.

Write your answers in the spaces below. Use full sentences.

1. Explain what happens to electrons when a plastic ruler is rubbed with a piece of wool. Which material becomes positively charged and which becomes negatively charged?

2. State the rule for attraction and repulsion between charged objects. Give one real-life example of each.

3. Why are protons NOT transferred during friction, but electrons are?

4. Explain in terms of electron transfer how a thunder cloud becomes charged during a thunderstorm.

5. Why does static electricity cause more shocks on dry days than on humid days?

6. List three safety precautions you should take during a lightning storm. Explain the science behind ONE of them.

7. A learner rubs different pairs of materials together and uses an electroscope to measure the charge each material ends up with. Her results are shown below.

Trial	Material A	Material B	Charge on A	Charge on B
1	Glass rod	Silk cloth	Positive (+)	Negative (−)
2	Rubber balloon	Wool jumper	Negative (−)	Positive (+)
3	Acrylic ruler	Wool cloth	Negative (−)	Positive (+)
4	Glass rod	Wool jumper	Positive (+)	Negative (−)

(a) In Trials 2 and 3, wool becomes positively charged. In Trial 4, wool becomes negatively charged. Is this a contradiction? Explain what this tells you about whether a material's charge depends only on the material itself, or also on what it is rubbed against. (2)
(b) In each trial, state which material LOST electrons and which material GAINED electrons. (1)
(c) Based on the pattern in the table, predict what charge glass would get if rubbed directly with an acrylic ruler. Use the results from Trials 3 and 4 to justify your prediction. (2)