O-Level and SEC G3 Physics K323
P13: Static Electricity
Model charge transfer, attraction, repulsion, fields, induction, hazards, and discharge without confusing charge with current.
Reviewed for the 2027 cohort on 19 July 2026. The official syllabus remains authoritative for assessable wording and paper details.
Core notes
Static electricity concerns charge at rest, electron transfer, electric fields, induction, hazards and useful applications such as electrostatic precipitation.
Charge and electric fields
Charge can be positive or negative and is measured in coulombs. Like charges repel and unlike charges attract. An electric field is a region where a charge experiences an electric force.
Field direction is the force direction on a positive test charge. Lines point away from a positive point charge and towards a negative point charge. Between two charges, line shape and spacing represent direction and relative field strength.
Charging by rubbing and induction
Charging by rubbing transfers electrons between materials. Protons remain bound in nuclei. An object that gains electrons becomes negatively charged; one that loses electrons becomes positively charged.
In induction, a nearby charge redistributes mobile electrons in a conductor without initial contact. With an earthing step and correct sequence, the conductor can retain a net charge opposite to the inducing charge after the earth and inducer are removed in the correct order.
Hazards and precipitators
Charge accumulation can produce sparks near flammable vapour or damage electronic components. Grounding, humidification, bonding and controlled discharge reduce the hazard by giving charge a safe path.
An electrostatic precipitator charges smoke particles, then attracts them to oppositely charged or earthed collector plates. The collected particles are removed, reducing particulate pollution from the exhaust stream.
Formulae and relationships
This chapter is assessed mainly through models, field patterns and explanations. Build the causal chain before adding any calculation.
Worked examples
Example 1: A neutral metal sphere is brought near a negatively charged rod. Explain the initial attraction without contact.
- Electrons in the sphere are repelled to the far side.
- The near side is left with induced positive charge while the sphere remains neutral overall.
- The opposite charge is closer, so its attraction exceeds the repulsion from the farther negative side.
Answer: Charge separation by induction produces a net attractive force.
Chapter checkpoint
Use these three moves to organise the topic before attempting a mixed or practical question.
- Track electron transfer and distinguish charging from creating charge.
- Use attraction, repulsion, induction, and field direction without treating charge as current.
- Explain discharge hazards and protection through charge movement and grounding.
Official outcome coverage
K323 P13: 9 mapped outcomes, references P13(a), P13(b), P13(c), P13(d), P13(e), P13(f), P13(g), P13(h), P13(i). Check the official K323 syllabus.
The outcome wording is not reproduced here. The relevant official syllabus remains authoritative for exact assessable scope.
Practical and data connection
Use a charged-object demonstration to separate the observed motion from the inferred sign and redistribution of charge.
Exam traps and retrieval check
Avoid these traps
- Saying positive charges move through an ordinary metal during rubbing.
- Drawing electric field arrows in the direction an electron would move.
- Assuming attraction alone proves that both objects have opposite net charges.
Check from memory
What moves during charging by rubbing?
Electrons.
Which way do field lines point around a negative charge?
Towards the charge.
What does a precipitator remove?
Charged solid or liquid particles from a gas stream.
Pure versus Combined scope
Combined Physics revisits part of this core under CP12 Electric Charges and Current of Electricity, but with reduced outcome scope. Combined students should follow the component checklist rather than assume every K323 outcome is assessable.
Shared explanation source
Eclat has a related explanation in its existing IP library. It can help with the shared concept, but its IP extensions and school-sensitive scope are not automatically part of K323. Open the related IP explanation.