Static charge - Teacher Slides.pptx

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Static charge

Electricity

Lesson 9 of 10

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Warm-up

Electricity

Lesson 9 of 10

Answer each one, then check.

1

What charge do electrons have?

2

What is an insulator?

3

What is a non-contact force?

4

What charge does a proton have?

5

Like charges...

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Warm-up - Answers

Electricity

Lesson 9 of 10

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

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Learning Objectives

Electricity

Lesson 9 of 10

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.

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Electricity

Lesson 9 of 10

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.

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Charging by Rubbing

Electricity

Lesson 9 of 10

Only electrons move; protons stay in the nuclei.

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Explaining Charging

Electricity

Lesson 9 of 10

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.

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Sparking

Electricity

Lesson 9 of 10

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.

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Evidence of Non-Contact Forces

Electricity

Lesson 9 of 10

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.

Hanging balls

Suspended charged balls move apart or together without touching.

Balloon on a wall

A rubbed balloon can stick to a wall.

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Common Mistakes

Electricity

Lesson 9 of 10

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'.

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Key Terms

Electricity

Lesson 9 of 10

Static electricity

Charge that builds up on an insulator.

Electron

A negatively charged particle.

Non-contact force

A force between objects that are not touching.

Earthing

Connecting to the ground so charge can flow away.

Repel

Push apart.

Attract

Pull together.

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Electricity

Lesson 9 of 10

YOUR TASK

Rub and Predict

10 minutes

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.

WHAT 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.

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Can I...?

Electricity

Lesson 9 of 10

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.

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Summary & Exam Focus

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.

EXAM FOCUS

Explain how a polythene rod becomes negatively charged when rubbed with a cloth. (3 marks)

Say which way the electrons move.

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Exam Practice: Static charge

Electricity

Lesson 9 of 10

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.

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Exam Practice: Static charge (cont.)

Electricity

Lesson 9 of 10

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.

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Question 1 · 3 marks · Explain

Electricity

Lesson 9 of 10

“

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.

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Question 1 · mark scheme

Electricity

Lesson 9 of 10

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

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Question 2 · 3 marks · Use the diagram

Electricity

Lesson 9 of 10

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

Electricity

Lesson 9 of 10

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

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Question 3 · 3 marks · Explain

Electricity

Lesson 9 of 10

“

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.

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Question 3 · mark scheme

Electricity

Lesson 9 of 10

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

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Question 4 · 2 marks · Explain

Electricity

Lesson 9 of 10

“

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.

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Question 4 · mark scheme

Electricity

Lesson 9 of 10

2 marks available. Award a mark for each point made.

Non-contact force

1 mark

Attraction between charged balloon and wall

1 mark

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Question 5 · 4 marks · Explain

Electricity

Lesson 9 of 10

“

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.

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Question 5 · mark scheme

Electricity

Lesson 9 of 10

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

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