Poles and magnetic fields - Teacher Slides.pptx

AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Poles and magnetic fields

Magnetism and electromagnetism

Lesson 1 of 8

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Warm-up

Magnetism and electromagnetism

Lesson 1 of 8

Answer each one, then check.

1

Name a magnetic material.

2

What is a force?

3

What is a non-contact force?

4

What do we call the ends of a magnet?

5

What do we use to find north?

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Warm-up - Answers

Magnetism and electromagnetism

Lesson 1 of 8

1

Name a magnetic material.

Iron, steel, nickel or cobalt

2

What is a force?

A push or a pull

3

What is a non-contact force?

A force acting without objects touching

4

What do we call the ends of a magnet?

Poles

5

What do we use to find north?

A compass

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Learning Objectives

Magnetism and electromagnetism

Lesson 1 of 8

1

Describe the forces between magnetic poles.

2

Describe permanent and induced magnets.

3

Describe the magnetic field of a bar magnet and draw its field lines.

4

Explain how a compass shows the direction of a magnetic field and why it shows the Earth has a magnetic field.

5

Describe how to plot a magnetic field with a compass.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Magnetism and electromagnetism

Lesson 1 of 8

MAGNETIC POLES

Like poles repel and unlike poles attract. These forces are non-contact forces. A magnetic field is the region around a magnet where a force acts on another magnet or on a magnetic material.

The force is strongest at the poles, where the field lines are closest together. Field lines point from north to south outside the magnet.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Magnetic Field of a Bar Magnet

Magnetism and electromagnetism

Lesson 1 of 8

Field lines are closest at the poles.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Plotting a Magnetic Field with a Compass

Magnetism and electromagnetism

Lesson 1 of 8

Mark each end of the needle, then move the compass.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Permanent or Induced?

Magnetism and electromagnetism

Lesson 1 of 8

PERMANENT MAGNET

• Always has its own magnetic field.

• Made of hard magnetic material.

• Can attract AND repel another magnet.

INDUCED MAGNET

• Becomes a magnet only while in another magnetic field.

• Made of a magnetic material such as iron.

• Always ATTRACTED to the magnet; loses most magnetism when removed.

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Magnetic Forces

Magnetism and electromagnetism

Lesson 1 of 8

Learn the rules.

Situation

What happens

North and south poles near each other

Attract

Two north poles (or two south poles)

Repel

A magnet near an unmagnetised iron nail

Nail becomes an induced magnet and is attracted

Compass needle near a magnet

Needle lines up with the field

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Why a Compass Points North

Magnetism and electromagnetism

Lesson 1 of 8

Explain why the needle of a compass points towards the Earth's north.

1

The compass needle

A small bar magnet free to turn

2

The Earth

Has its own magnetic field, like a giant bar magnet

3

Result

The needle lines up with the Earth's field and points along it

ANSWER

The Earth has a magnetic field and the needle aligns with it.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Key Points

Magnetism and electromagnetism

Lesson 1 of 8

Learn these.

Direction

Field lines run from north to south outside the magnet.

Strength

Stronger where the lines are closer together.

Distance

The field gets weaker as you move away.

Magnetic materials

Iron, steel, cobalt and nickel.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Key Terms

Magnetism and electromagnetism

Lesson 1 of 8

Magnetic pole

The end of a magnet where the force is strongest.

Magnetic field

The region around a magnet where a force acts on another magnet or a magnetic material.

Permanent magnet

A magnet that always produces its own magnetic field.

Induced magnet

A material that becomes magnetic only when in a magnetic field.

Field line

A line showing the direction of the force on a north pole.

Compass

A small magnet that lines up with a magnetic field.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Magnetism and electromagnetism

Lesson 1 of 8

YOUR TASK

Field Lines

10 minutes

Sketch the field lines between a north pole and a south pole facing each other, then between two north poles. Add arrows.

1

Lines leave N, enter S.

2

Lines never cross.

WHAT A GOOD ANSWER SHOWS

Between N and S: lines run from N to S across the gap. Between two N poles: lines curve away from each other and never join.

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Can I...?

Magnetism and electromagnetism

Lesson 1 of 8

State the rules for poles.

Describe permanent and induced magnets.

Name magnetic materials.

Draw a bar magnet field.

Put arrows on field lines.

Describe a compass.

Explain the Earth's field.

Describe plotting a field.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Summary & Exam Focus

Like poles repel, unlike poles attract.

Field lines run north to south.

Induced magnets are always attracted.

A compass shows the Earth has a magnetic field.

EXAM FOCUS

Explain why an iron nail is attracted to a magnet. (2 marks)

The nail becomes an induced magnet.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Exam Practice: Poles and magnetic fields

Magnetism and electromagnetism

Lesson 1 of 8

Answer all questions. Use the mark allocation as a guide to how much to write. · 14 minutes

Question 1 · 2 marks · State

State what happens when (a) two north poles are brought together and (b) a north pole and a south pole are brought together.

Question 2 · 2 marks · Describe

What is the difference between a permanent magnet and an induced magnet?

Question 3 · 3 marks · Explain

A student brings one end of a bar of iron near a magnet. The iron is attracted. Explain why the iron is always attracted and never repelled.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Exam Practice: Poles and magnetic fields (cont.)

Magnetism and electromagnetism

Lesson 1 of 8

Question 4 · 4 marks · Describe

Describe how you would use a plotting compass to plot the magnetic field of a bar magnet.

Question 5 · 2 marks · Explain

A compass needle points north. Explain what this tells you about the Earth.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Question 1 · 2 marks · State

Magnetism and electromagnetism

Lesson 1 of 8

“

State what happens when (a) two north poles are brought together and (b) a north pole and a south pole are brought together.

HOW TO ANSWER IT

Command word: State. Worth 2 marks, so plan before writing.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Question 1 · mark scheme

Magnetism and electromagnetism

Lesson 1 of 8

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

Repel

1 mark

Attract

1 mark

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Question 2 · 2 marks · Describe

Magnetism and electromagnetism

Lesson 1 of 8

“

What is the difference between a permanent magnet and an induced magnet?

HOW TO ANSWER IT

Command word: Describe. Worth 2 marks, so plan before writing.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Question 2 · mark scheme

Magnetism and electromagnetism

Lesson 1 of 8

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

Permanent: always magnetic

1 mark

Induced: only magnetic in a field

1 mark

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Question 3 · 3 marks · Explain

Magnetism and electromagnetism

Lesson 1 of 8

“

A student brings one end of a bar of iron near a magnet. The iron is attracted. Explain why the iron is always attracted and never repelled.

HOW TO ANSWER IT

Command word: Explain. Worth 3 marks, so plan before writing.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Question 3 · mark scheme

Magnetism and electromagnetism

Lesson 1 of 8

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

Iron becomes an induced magnet

1 mark

Nearest end is the opposite pole

1 mark

Unlike poles attract

1 mark

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Question 4 · 4 marks · Describe

Magnetism and electromagnetism

Lesson 1 of 8

“

Describe how you would use a plotting compass to plot the magnetic field of a bar magnet.

HOW TO ANSWER IT

Command word: Describe. Worth 4 marks, so plan before writing.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Question 4 · mark scheme

Magnetism and electromagnetism

Lesson 1 of 8

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

Magnet on paper, compass near a pole

1 mark

Mark both ends of the needle

1 mark

Move compass along and repeat; join the dots

1 mark

Repeat from other starting points and add arrows from north to south

1 mark

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Question 5 · 2 marks · Explain

Magnetism and electromagnetism

Lesson 1 of 8

“

A compass needle points north. Explain what this tells you about the Earth.

HOW TO ANSWER IT

Command word: Explain. Worth 2 marks, so plan before writing.

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AQA GCSE PHYSICS · PAPER 2 · FOUNDATION & HIGHER

Question 5 · mark scheme

Magnetism and electromagnetism

Lesson 1 of 8

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

Needle lines up with a magnetic field

1 mark

The Earth has a magnetic field

1 mark

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