Grade 7 Integrated Science FORCE AND ENERGY – Static Electricity Notes
Integrated Science — Force and Energy
Subtopic: Static Electricity (Age 12)
- Describe what static electricity is.
- Explain how objects become charged (by friction, contact and induction).
- Do simple investigations to see attraction and repulsion of charged objects.
- Identify safe and everyday uses of static electricity.
What is static electricity?
Static electricity is the electric charge that stays on the surface of an object. It is called "static" because the charge does not flow like the electric current in a wire. Static charge happens when tiny particles called electrons move from one object to another.
Why does it happen? (Simple explanation)
All matter is made of atoms. Atoms have electrons (negative) and protons (positive). When two different materials rub together, electrons can move from one material to the other. The object that gains electrons becomes negatively charged. The object that loses electrons becomes positively charged.
Key ideas (short)
- Electrons move; protons stay in the atom’s centre.
- Like charges repel (– repels –, + repels +). Unlike charges attract (– attracts +).
- Insulators (plastic, rubber, dry hair) hold charge; conductors (metal) allow charges to move away.
A simple picture: Balloon and wall
Rubbing a balloon on your hair transfers electrons to the balloon. The balloon becomes negative and the wall near it becomes slightly positive by induction, so the balloon sticks.
– –
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How to charge objects (three ways)
- By friction — rubbing two objects (e.g., balloon and hair) so electrons move.
- By contact (conduction) — touching a charged object to another object transfers charge.
- By induction — a charged object brought near a conductor causes charges to move inside the conductor without touching.
Simple class experiments (materials easy to find)
Materials: balloon, small pieces of paper or tissue.
Steps:
- Blow up and tie the balloon.
- Rub the balloon on your hair or a wool jumper for about 10 seconds.
- Hold the balloon near small pieces of paper on a table.
What you see: the paper pieces jump up and stick to the balloon. The balloon has become negatively charged and attracts the neutral paper.
Materials: plastic comb, tissue paper pieces.
Steps: Comb dry hair several times, then bring the comb near small paper pieces.
What you see: the comb picks up the paper — showing attraction between opposite/neutral charges.
Explanation of observations
When you rub the balloon or comb, electrons move and the object becomes negatively charged. Neutral paper becomes attracted because charges move slightly so the nearer side becomes slightly positive (this is called induction). Opposite charges attract.
Conductors and insulators — examples
- Conductors: copper, aluminium, water with salt, your body (metal objects let charges move away).
- Insulators: plastic, rubber, dry wood, glass (these hold static charge well).
Safety and interesting facts
- Static shocks (small spark) can be painful. Avoid building big static charges near flammable liquids or gases.
- Lightning is a large form of static electricity — very dangerous. Lightning conductors protect buildings.
- Static electricity is used in spray painting and photocopying machines to move paint or toner.
Quick check questions (try these)
- What moves when an object becomes charged: protons or electrons?
- Why does a rubbed balloon stick to a wall?
- Is metal a good place to keep static charge? Why or why not?
Glossary (simple)
- Static electricity — electric charges that stay on a surface.
- Electron — small negative particle in an atom.
- Friction — rubbing two objects together.
- Induction — bringing a charged object near another so charges separate without touching.
- Conductor — material that lets electric charge move easily.
- Insulator — material that does not let electric charge move easily.
Try the balloon experiment and change these things. Record what happens:
- Use a dry room and then a wet/humid day — which works better?
- Use wool cloth vs cotton cloth to rub the balloon — which gives more charge?
- Test if the charged balloon will pick up aluminium foil bits or a wet piece of paper.
Summary: Static electricity is caused by the movement of electrons. Rubbing objects, touching charged objects, and using induction can make objects attract or repel. Try safe experiments to see the effects for yourself.
End of notes