This mini-lesson walks you through the whole of Edexcel Topic 11 — Static electricity: how insulators are charged by friction, why electrons (never protons) move, the forces between charges, induction, earthing, the everyday uses and dangers of static, and electric fields.
Work through each screen, answer the questions as you go (some are wordy, some are sorting games) and collect ⭐ stars. Press Start when you're ready.
11.1 · Charging by friction
Rub it and it charges up
An insulator can be charged by friction. When two insulators are rubbed together, electrons are dragged from one onto the other. Only the tiny, light, negatively charged electrons move — the protons are locked in the nuclei and never move.
Rub a polythene rod with a duster: electrons jump from the rod onto the cloth. The cloth becomes negative; the rod is left positive.
Watch out: it is always the electrons that move, never the protons. An object does not "gain plus charge" — it becomes positive only because it has lost electrons.
Quick check
Which way do the electrons go?
?A perspex rod is rubbed with a cloth. Afterwards the rod is positively charged. What must have happened?
11.2 · Equal and opposite
Charge is conserved
Rubbing doesn't create charge — it just moves electrons from one object to the other:
The material that gains electrons becomes negatively charged.
The material that loses the same electrons is left equally positively charged.
So the two objects always end up with equal and opposite charges — the total charge is unchanged. This is the conservation of charge.
Six electrons leave one object and arrive on the other — so the charges are −6 and +6: equal in size, opposite in sign.11.3 · Forces between charges
Like repel, unlike attract
Charged objects exert a non-contact force on each other — they push or pull without touching:
Like charges repel (+ and +, or − and −).
Unlike charges attract (+ and −).
Two positives push apart (repel); a positive and a negative pull together (attract). The force acts at a distance, with no contact.Sort it
Attract or repel?
Tap the correct outcome for each pair of charged objects.
11.4 · Everyday static
Why a charged rod picks up paper
Many everyday effects are explained by the movement of electrons:
Shocks — you build up charge (e.g. walking on carpet), then discharge through a doorknob.
Lightning — huge charge separates in storm clouds, then a giant spark earths it.
A charged balloon sticking to a wall, and a charged rod/comb picking up small bits of paper — these work by induction.
A charged object attracts a neutral object by inducing charge separation: it repels the like charge in the paper to the far side and pulls the opposite charge to the near side. The near (opposite) charge is closer, so attraction wins and the paper jumps up.
The negative rod pushes the paper's electrons to the far side, leaving the near side positive. The closer + side is pulled towards the rod, so the paper is attracted.
Key idea: a charged object can attract a neutral object — it does not need to be oppositely charged. This is attraction by induction.
Quick check
Lifting the paper
?A charged plastic comb is held just above some tiny uncharged pieces of paper, which jump up to it. Why are the neutral pieces attracted?
11.5 · Earthing
Earthing removes excess charge
Earthing connects a charged object to the ground with a conductor, so excess charge is removed by the movement of electrons:
A negatively charged object has too many electrons — they flow down to earth until it is neutral.
A positively charged object is short of electrons — electrons flow up from earth onto it until it is neutral.
A negatively charged object earthed: the surplus electrons flow down the wire to earth, leaving the object neutral. (For a positive object, electrons flow the other way — up from earth.)Quick check
Earthing a positive object
?A metal sphere carries a positive charge. It is then earthed with a wire. Which way do electrons move, and what happens to the sphere?
11.6 · Uses of static
Putting static to work
Static charge is genuinely useful when you want an even, all-round coating:
Insecticide / crop sprayers — droplets are charged the same, so they spread out (repel) into a fine, even mist and are attracted all around each plant.
Paint spraying (e.g. cars/bikes) — the paint is charged and the object earthed, so paint wraps round and coats even the hidden sides, wasting less.
Inkjet printers — tiny charged ink drops are steered by charged plates onto the right spot.
Like-charged droplets repel each other into a fine, even spread, and are attracted to the earthed object all over — coating even the back.11.7 · Dangers of static
When sparking is dangerous
A big build-up of charge can suddenly spark as it discharges. Near flammable fuel or vapour, that spark can cause an explosion:
Refuelling aircraft or fuel tankers — fuel flowing through pipes rubs and builds up charge, which could spark and ignite the fuel vapour.
Filling cars at a petrol station — the same risk on a smaller scale.
The cure is earthing and bonding: a conducting wire connects the tanker/aircraft to earth (and to the fuel source), so charge leaks safely away by the movement of electrons before it can build up enough to spark.
Bonding and earthing let electrons flow away continuously, so no dangerous charge builds up and no spark forms.Quick check
Stopping the spark
?Before fuel is pumped into an aircraft, the aircraft is connected to earth and to the fuel pipe with a conducting wire. Why?
11.8 · Electric field
What is an electric field?
An electric field is a region where an electric charge experiences a force.
electric field = a region where a charge feels a forceAny other charge placed in the field is pushed or pulled — that's how charges act at a distance.
We draw the field with field lines:
The lines point in the direction of the force on a positive charge — so they go from + to −.
Where the lines are closer together, the field is stronger.
11.9 · Field shapes
Point charge and parallel plates
You need to know two field patterns. Arrows run + → −, and the line density shows the strength:
Around a point charge the field is radial — strongest near the charge (lines closest there). Between parallel plates the field is uniform — equally spaced lines, all pointing from the + plate to the − plate.Quick check
Which way do field lines point?
?For the electric field around an isolated positive point charge, in which direction do the field lines point, and where is the field strongest?
11.10 · The field explains it all
Using fields to explain static
The electric-field idea ties the whole topic together:
Attraction / repulsion: one charge sits in the field of the other, so it feels a force — repelled if like, attracted if unlike.
Sparking: when charge builds up, the field gets very strong. If it is strong enough it ionises the air (rips electrons off air molecules), turning it into a conductor. Charge then rushes across as a spark — that's a tiny lightning bolt.
Once the field between charges is strong enough to ionise the air, the gap becomes conducting and a spark discharges the charge across it.Sort it
Gained or lost electrons?
Each object below has been charged. Tap an object, then tap the box for how it got its charge.
➖ Gained electrons (negative)
➕ Lost electrons (positive)
Quick check
Static vs current electricity
?What is the key difference between static electricity and the current electricity in a circuit?
Recap
The big ideas to know
Charging by friction: insulators charge as electrons transfer (11.1).