IP Physics Notes (Upper Secondary, Year 3-4): 10) Static Electricity

Study guide30 Sep 2025, 00:00 ZUpdated 30 Nov 2025

Charging methods, electric field patterns, real-world applications, and safety for static electricity questions.

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Q: What does IP Physics Notes (Upper Secondary, Year 3-4): 10) Static Electricity cover?
A: Charging methods, electric field patterns, real-world applications, and safety for static electricity questions.

Quick recap -- Static electricity tracks how charges accumulate, move, and interact via electric fields. Watch electron transfer, sketch field lines correctly, and relate the principles to photocopiers, paint sprayers, and safety controls.

The core idea is simple: Static electricity is about where electrons move and where charge builds up.

Use it as a working check: Track electron transfer for charging, use field lines to show force direction, and connect sparks or attraction to grounding, humidity, and safety controls.

Then go one layer deeper: Use the field sketches, suspended-sphere example, and applications list to practise explaining charging method, field pattern, useful effect, and hazard control in one chain.

Keep your practice loop tight via our IP Physics tuition hub-it links each topic here to quizzes, diagnostics, and WA-style problem sets.

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These notes align with SEAB GCE O-Level Physics (6091) content used in IP programmes (exams from 2026).

Status: SEAB O-Level Physics 6091 syllabus (exams from 2026) checked 2025-11-30 - scope unchanged; remains the reference for these notes.

Charge Basics

Charge comes in positive or negative units; SI unit coulomb $\pu{C}$ .
Like charges repel; unlike charges attract.
Conservation of charge: total charge in an isolated system stays constant.
Only electrons move in everyday charging processes; protons remain fixed in nuclei.
Charging methods:
- Friction: electrons transferred between insulators (e.g., polythene rod and wool).
- Conduction: direct contact lets electrons flow between conductors.

Reviewed by

Chee Wei Jie·Academic Advisor (Physics)

Method	Contact needed?	What electrons do	Final-charge clue
Friction	Yes, between rubbed insulators	Electrons transfer from one material to the other.	The two objects end with opposite charges.
Conduction	Yes, charged object touches conductor	Electrons flow until charge is shared.	The touched object usually gains the same type of charge as the charging object.
Induction with earthing	No contact with the charged object	Electrons are repelled or attracted, then earthing lets electrons enter or leave.	The conductor is left with the opposite charge after the earth connection and inducing object are removed in the correct order.
Polarisation only	No	Electrons shift slightly within a neutral object.	The object can be attracted even though its net charge is still zero.

Step	What happens	What to say in the explanation
Bring the charged object near	Charges in the neutral conductor redistribute.	The conductor is polarised, but it is still neutral overall.
Earth the conductor while the charged object is still nearby	Electrons enter or leave through the earth connection.	Earthing provides a path for mobile electrons.
Remove the earth connection first	The electron imbalance is trapped on the conductor.	The conductor now has a net charge.
Remove the charged object last	The trapped charge spreads over the conductor.	The final charge is opposite to the inducing object's charge.

Property	Insulators	Conductors
Electron mobility	Electrons localised	Electrons free to move
Charging	Build charge by friction; charge stays localised	Charge spreads across surface; easy to discharge
Examples	Plastic, glass, rubber	Metals, graphite
Discharging	Hold charge until grounded	Lose charge quickly when earthed

Situation	First sketch move	What spacing shows	Common trap
Single positive charge	Draw radial arrows pointing away from the charge.	Lines are closer near the charge, so the field is stronger there.	Drawing arrows toward a positive charge.
Single negative charge	Draw radial arrows pointing toward the charge.	Same radial crowding rule as a positive charge.	Changing the spacing rule just because the charge is negative.
Two unlike charges	Draw lines from the positive charge to the negative charge.	Lines are denser between nearby opposite charges.	Letting field lines cross at the middle.
Parallel plates	Draw straight, equally spaced arrows from positive plate to negative plate.	Equal spacing represents a near-uniform field between plates.	Curving lines in the central region without a reason.
Charged conductor	Make lines meet the surface at right angles.	Closer lines near sharper parts show stronger local field.	Drawing field lines along the conductor surface.

Force	Direction on the sphere	Equation role	Common trap
Weight $mg$	Vertically downward	Balanced by the vertical component of tension.	Putting weight along the thread.
Tension $T$	Along the thread towards the support	Split into $T\cos\theta$ vertically and $T\sin\theta$ horizontally when $\theta$ is measured from the vertical.	Swapping sine and cosine.
Electric force $F_\text{electric}$	Horizontally away from the other like-charged sphere, or towards an unlike charge	Balanced by the horizontal component of tension.	Adding it to weight instead of resolving perpendicular directions.

IP Physics Notes (Upper Secondary, Year 3-4): 10) Static Electricity

Charge Basics

Charging method checkpoint

Induction with earthing sequence checkpoint

Conductors vs Insulators

Electric Fields

Field sketch checkpoint

Suspended-sphere force checkpoint

Worked Example: Force Between Suspended Spheres

Applications of Static Electricity

Hazards & Safety

Practice Quiz

Key Takeaways

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