AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER
Static charge
Electricity · Lesson 9 of 10
Teacher copy - includes the notes for whoever is teaching from it.
Warm-up
Answer each one, then check.
1. What charge do electrons have?
Negative
2. What is an insulator?
A material that does not conduct electricity
3. What is a non-contact force?
A force between objects that are not touching
4. What charge does a proton have?
Positive
5. Like charges...
Repel
Learning Objectives
1. Describe the production of static electricity by rubbing.
2. Explain charging in terms of the transfer of electrons.
3. Describe evidence that charged objects exert non-contact forces.
4. Explain sparking.
Static Electricity
When insulating materials are rubbed together, electrons are transferred: the material that gains electrons becomes negatively charged and the one that loses them is left with an equal positive charge.
Objects with the same type of charge repel; objects with different types of charge attract.
Charging by Rubbing
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Only electrons move; protons stay in the nuclei. |
A polythene rod rubbed with a cloth gaining electrons, and pairs of charged balls attracting or repelling.
Explaining Charging
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Explain why a polythene rod becomes negatively charged when rubbed with a cloth. |
1. Friction
Rubbing transfers energy so electrons can move
2. Electrons move
Negatively charged electrons are rubbed off the cloth and on to the rod
3. The rod
Gains electrons, so it becomes negatively charged
4. The cloth
Loses electrons and is left with an equal positive charge
Answer: Electrons transfer from the cloth to the rod; the rod becomes negative and the cloth positive.
Sparking
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Explain how a spark can jump from a charged object to an earthed conductor. |
1. Charge builds
A large amount of charge collects on the object
2. Strong field
The electric field between the object and the conductor becomes very strong
3. Air ionises
The air becomes ionised and conducts, so charge flows as a spark
Answer: Charge builds up until the field is strong enough to make air conduct, and the charge flows as a spark.
Evidence of Non-Contact Forces
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Repulsion Two charged rods of the same charge push each other apart. |
Attraction A charged rod attracts small pieces of paper or a stream of water. |
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Hanging balls Suspended charged balls move apart or together without touching. |
Balloon on a wall A rubbed balloon can stick to a wall. |
Common Mistakes
Be precise.
▸ Only electrons move. Positive charges (protons) are fixed in the nucleus and do not move when rubbed.
▸ Insulators. Only insulators keep the charge; a metal rod held in the hand loses its charge.
▸ Say gained or lost. Say 'gained electrons', not 'gained negative charge'.
Key Terms
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Static electricity Charge that builds up on an insulator. |
Electron A negatively charged particle. |
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Non-contact force A force between objects that are not touching. |
Earthing Connecting to the ground so charge can flow away. |
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Repel Push apart. |
Attract Pull together. |
Your Task: Rub and Predict
10 minutes
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A student rubs a cloth on a balloon. The balloon is then attracted to the wall. Explain what has happened to the electrons and what type of charge the balloon has. 1. Say which way electrons moved. 2. State the charge on each object. |
A good answer shows: Electrons are transferred from the cloth to the balloon. The balloon gains electrons and becomes negatively charged; it attracts the wall.
Note: Ask what would happen if two rubbed balloons were held close together.
Can I...?
☐ Explain how rubbing makes charge.
☐ Say which particles move.
☐ State the charge on each object.
☐ Describe attraction and repulsion.
☐ Describe evidence for non-contact forces.
☐ Explain sparking.
☐ Explain why insulators keep charge.
☐ Use the terms gained and lost electrons.
Summary
✓ Rubbing insulators transfers electrons.
✓ The material that gains electrons is negative; the one that loses electrons is positive.
✓ Like charges repel, unlike attract.
✓ Sparks occur when the field is strong enough to ionise air.
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EXAM FOCUS Explain how a polythene rod becomes negatively charged when rubbed with a cloth. (3 marks) Say which way the electrons move. |
Exam Practice: Static charge
Answer all questions. Use the mark allocation as a guide to how much to write. · 16 minutes
▸ Question 1 · 3 marks · Explain. A polythene rod is rubbed with a cloth and becomes negatively charged. Explain how the rod becomes negatively charged.
▸ Question 2 · 3 marks · Use the diagram. The diagram shows two charged balls hanging from threads. Ball A is negatively charged. (a) State the type of charge on ball B. (b) Name…
▸ Question 3 · 3 marks · Explain. A student walks across a nylon carpet and then gets a small electric shock when touching a metal door handle. Explain why.
▸ Question 4 · 2 marks · Explain. Explain why a charged balloon can stick to a wall even though the balloon and wall do not touch.
▸ Question 5 · 4 marks · Explain. Lightning is a very large spark. Explain how charge builds up in a cloud and what causes the lightning.
Question 1 · 3 marks · Explain
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“A polythene rod is rubbed with a cloth and becomes negatively charged. Explain how the rod becomes negatively charged.” |
HOW TO ANSWER IT Command word: Explain. Worth 3 marks, so plan before writing.
Question 1 · mark scheme
3 marks available. Award a mark for each point made.
▸ Electrons transferred. 1 mark
▸ From the cloth to the rod. 1 mark
▸ Rod gains electrons so it is negative. 1 mark
▸ Model answer. Electrons are transferred from the cloth to the rod when they are rubbed together. The rod gains electrons so it becomes negative.
Question 2 · 3 marks · Use the diagram
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The diagram shows two charged balls hanging from threads. Ball A is negatively charged. (a) State the type of charge on ball B. (b) Name the type of force acting between the balls. (3 marks) |
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Question 2 · mark scheme
3 marks available. Award a mark for each point made.
▸ Negative. 1 mark
▸ Because they repel (like charges). 1 mark
▸ Non-contact force. 1 mark
▸ Model answer. (a) Negative (they repel). (b) A non-contact force (electrostatic repulsion).
Question 3 · 3 marks · Explain
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“A student walks across a nylon carpet and then gets a small electric shock when touching a metal door handle. Explain why.” |
HOW TO ANSWER IT Command word: Explain. Worth 3 marks, so plan before writing.
Question 3 · mark scheme
3 marks available. Award a mark for each point made.
▸ Rubbing transfers electrons. 1 mark
▸ The student becomes charged. 1 mark
▸ Charge flows to earth through the handle. 1 mark
▸ Model answer. Electrons are rubbed off the carpet onto the student (or the other way round), so the student becomes charged. When the student touches the metal handle, charge flows through the metal to earth, causing a spark or shock.
Question 4 · 2 marks · Explain
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“Explain why a charged balloon can stick to a wall even though the balloon and wall do not touch.” |
HOW TO ANSWER IT Command word: Explain. Worth 2 marks, so plan before writing.
Question 4 · mark scheme
2 marks available. Award a mark for each point made.
▸ Non-contact force. 1 mark
▸ Attraction between charged balloon and wall. 1 mark
▸ Model answer. The charged balloon exerts a non-contact force (electrostatic force of attraction) on the wall.
Question 5 · 4 marks · Explain
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“Lightning is a very large spark. Explain how charge builds up in a cloud and what causes the lightning.” |
HOW TO ANSWER IT Command word: Explain. Worth 4 marks, so plan before writing.
Question 5 · mark scheme
4 marks available. Award a mark for each point made.
▸ Electrons transferred by collisions or friction. 1 mark
▸ Cloud charged, large pd between cloud and ground. 1 mark
▸ Strong electric field ionises the air. 1 mark
▸ Charge flows as a spark. 1 mark
▸ Model answer. Collisions between ice particles in the cloud transfer electrons, so parts of the cloud become charged. A large potential difference forms between the cloud and the ground. The electric field becomes strong enough to ionise the air, which conducts, and charge flows as lightning.