AQA GCSE Physics Foundation (8463), Foundation tier · Electricity › Static electricity
Practise Static charge. 5 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
How rubbing two insulating materials together charges them by transferring electrons, how charged objects attract or repel, and how sparks are produced. This is in GCSE Physics only, not Combined Science. Expect 'explain' questions using electron transfer and short questions on like and unlike charges.
Key facts
Rubbing insulating materials together transfers electrons
Gains electrons → negative charge
Loses electrons → equal positive charge
Only electrons (negative charges) move
Like charges repel; unlike charges attract
Forces between charged objects are non-contact forces
Large build-up of charge → spark to a nearby earthed conductor
Notes
Charging by rubbing
diagram
When certain insulating materials are rubbed against each other, they become electrically charged.
Negatively charged electrons are rubbed off one material and on to the other.
The material that gains electrons becomes negatively charged.
The material that loses electrons is left with an equal positive charge.
Only electrons move. The positive charges (protons, in the nuclei of the atoms) stay where they are.
Example: rubbing a polythene rod with a woollen cloth moves electrons from the cloth to the rod, so the rod becomes negative and the cloth becomes positive.
Only electrons move. The charges on the rod and the cloth are equal and opposite.
Forces between charged objects
diagram
When two charged objects are brought close together, they exert a force on each other.
Two objects with the same type of charge repel. Two objects with different types of charge attract.
These forces are non-contact forces: they act without the objects touching.
Evidence: hang a charged rod from a thread so it can turn freely. Bring another charged rod close to one end without touching it. The hanging rod turns away (repulsion) or turns towards it (attraction).
Like charges repel; unlike charges attract.
Sparking
Rubbing can build up a large charge on an object, e.g. on you when your shoes rub on a nylon carpet.
As the charge builds up, the potential difference between the object and a nearby earthed conductor (such as a metal tap) increases.
When the pd is large enough, charge jumps across the gap through the air. This is a spark.
How to answer each type of question
Explain how an object becomes charged
2 to 3 marksGrade 5
Say that rubbing transfers electrons.
Say which way the electrons move (from ... to ...).
Say that gaining electrons gives a negative charge, or losing electrons leaves a positive charge.
Example. A student rubs a polythene rod with a woollen cloth. The rod becomes negatively charged. Explain how the rod becomes negatively charged.
Show the model answerHide the model answer
Rubbing transfers electrons (1) from the cloth to the rod (1). The rod has gained electrons, which are negative, so it becomes negatively charged (1).
Predict and describe forces between charged objects
2 marksGrade 5
Work out the sign of each charge.
Same sign: repel (move apart). Different signs: attract (move together).
Describe what you would see, e.g. the hanging rod turns away from the other rod.
Example. A negatively charged polythene rod hangs from a thread so that it can turn freely. Describe what happens when each of these is brought close to one end, without touching: (a) another negatively charged polythene rod (b) a positively charged acetate rod.
Show the model answerHide the model answer
(a) The hanging rod turns away / is repelled, because like charges repel (1) (b) The hanging rod turns towards the acetate rod / is attracted, because unlike charges attract (1)
Don’t lose marks
Saying positive charges (protons) move from one material to the other. Only electrons move.
Saying a positively charged object 'gained protons'. It lost electrons.
Writing 'friction makes it charged' without saying that electrons are transferred.
Forgetting that the two materials end up with equal and opposite charges.
More tips
Memory tricks
Only electrons move: 'negatives move, positives stay'.
GAIN electrons = GAIN negative charge. LOSE electrons = left positive.
Opposites attract, likes repel, just like the poles of magnets (but these are charges, not poles).
Exam technique
Always use the word 'electrons' and say which way they move (from ... to ...).
Give every charge a sign: 'positive' or 'negative', never just 'charged' or 'more charge'.
For 'describe the evidence' questions, say what you see (turns towards / away) and that the objects do not touch.
What each grade needs
What you need to be able to do, from the first marks up to the top grade.
Grade 3
State how like and unlike charges interactThe same type of charge repels; different types of charge attract.
Grade 4
Describe charging by rubbing insulatorsRubbing certain insulating materials together makes them electrically charged.
Grade 5
Explain charging using electron transferElectrons move from one material to the other; the gainer becomes negative, the loser positive.
Grade 5
Describe evidence for forces between chargesA charged rod hanging freely turns towards or away from another charged rod that is not touching it.
Quick recall
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
What type of charge does the cloth have after it has been rubbed?
Positive
After rubbing, the student’s hairs move apart from each other. Explain why.
Each hair has the same type of charge (positive), and like charges repel.
Complete the sentence. Two objects with the same type of charge .................... each other.
repel
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
A student rubs a polythene rod with a woollen cloth. The rod becomes negatively charged.
(a) Which particles are transferred when the rod is rubbed with the cloth? Tick (✓) one box.[1]
atoms
electrons
neutrons
protons
(b) In which direction are the particles transferred? Tick (✓) one box.[1]
from the cloth to the rod
from the rod to the cloth
(c) What type of charge does the cloth have after it has been rubbed?[1]
(d) The student brings a second negatively charged polythene rod close to the first rod. The rods do not touch. What happens? Tick (✓) one box.[1]
The rods attract each other.
The rods repel each other.
Nothing happens.
Show the answer and mark scheme
(a)Answer: electrons
(b)Answer: from the cloth to the rod
(c)Answer: Positive
positive
(d)Answer: The rods repel each other.
Question 2Medium7 marks
A student rubs a balloon on their hair. The balloon becomes negatively charged.
(a) Explain how the balloon becomes negatively charged.[2]
(b) Explain why the student’s hair is attracted to the balloon.[2]
(c) After rubbing, the student’s hairs move apart from each other. Explain why.[2]
(d) The force between the balloon and the hair is a non-contact force. What is meant by a non-contact force?[1]
Show the answer and mark scheme
(a)Answer: Rubbing transfers electrons from the hair to the balloon; the balloon gains electrons, so it has a negative charge.
electrons are transferred / rubbed off (the hair) onto the balloon
the balloon gains electrons (which are negative)
(b)Answer: The hair has lost electrons so it has a positive charge; opposite (unlike) charges attract.
the hair has lost electrons so is positively charged
opposite / unlike charges attract
(c)Answer: Each hair has the same type of charge (positive), and like charges repel.
each hair has the same type of charge (positive)
like charges repel
(d)Answer: A force that acts between objects that are not touching.
a force that acts between objects that are not touching / physically separated