Energy stores and systems.pptx

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Energy stores and systems

Energy

Lesson 1 of 7

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Warm-up

Energy

Lesson 1 of 7

Answer each one, then check.

1

What is the unit of energy?

2

What is a system?

3

Name the energy store in a stretched spring.

4

Name the energy store in food and fuels.

5

Can energy be created or destroyed?

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Warm-up - Answers

Energy

Lesson 1 of 7

1

What is the unit of energy?

The joule (J)

2

What is a system?

An object or group of objects

3

Name the energy store in a stretched spring.

Elastic potential

4

Name the energy store in food and fuels.

Chemical

5

Can energy be created or destroyed?

No, it can only be transferred, stored or dissipated

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Learning Objectives

Energy

Lesson 1 of 7

1

Define a system and describe changes in the way energy is stored when a system changes.

2

Name the main energy stores and the four transfer pathways.

3

Describe the energy changes in common situations, such as an object projected upwards or a kettle boiling water.

4

Write clear statements using the phrase 'energy is transferred from ... to ...'.

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Energy

Lesson 1 of 7

CONSERVATION OF ENERGY

Energy cannot be created or destroyed. It can be transferred usefully, stored or dissipated.

A system is an object or group of objects. When a system changes, there are changes in the way energy is stored.

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Energy Changes in Two Systems

Energy

Lesson 1 of 7

Ask 'which store goes down and which goes up?' for every change.

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

The Energy Stores

Energy

Lesson 1 of 7

Learn the main stores and an example of each.

Energy store

Examples

Kinetic

Any moving object

Gravitational potential

An object above the ground

Elastic potential

A stretched or compressed spring, an elastic band

Thermal

A hot object; the particles have more energy

Chemical

Fuels, food, batteries

Nuclear

The nucleus of an atom

Magnetic

Magnets and electromagnets

Electrostatic

Charged objects, such as a charged balloon

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Ways Energy Is Transferred

Energy

Lesson 1 of 7

Mechanically

A force moves an object through a distance (work done).

Electrically

Charge flows in a circuit (work done by the current).

By heating

Energy flows from a hotter object to a cooler one.

By radiation

Energy is carried by waves, such as light and sound.

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

A Ball Thrown Upwards

Energy

Lesson 1 of 7

Describe the changes in the way energy is stored when a ball is thrown upwards, until it reaches its highest point.

1

Just after leaving the hand

The ball has a large kinetic energy store

2

As it rises

It slows down, so the kinetic energy store decreases

3

At the same time

Its height increases, so the gravitational potential energy store increases

4

Small effect

Some energy is transferred to the thermal store of the air by friction

ANSWER

Energy is transferred mechanically from the kinetic store to the gravitational potential store, with a little dissipated to the thermal store of the air.

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Boiling Water in a Kettle

Energy

Lesson 1 of 7

Describe the changes in the way energy is stored when a kettle boils water.

1

Electrical work

Charge flowing through the heating element transfers energy from the mains

2

Heating element

The thermal energy store of the element increases

3

By heating

Energy is transferred to the thermal energy store of the water, which increases

4

Wasted

Some energy heats the kettle and the surroundings

ANSWER

Energy is transferred electrically and then by heating to the thermal store of the water; some is dissipated to the surroundings.

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Writing Good Answers

Energy

Lesson 1 of 7

Use the language of stores and transfers.

Name the stores

Say 'the kinetic energy store decreases', not 'kinetic energy is lost'.

Say how

Give the pathway: mechanically, electrically, by heating or by radiation.

Say where the rest goes

Mention dissipation to the surroundings if the system is not perfectly efficient.

Total energy

The total energy after the change is the same as before.

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Key Terms

Energy

Lesson 1 of 7

System

An object or group of objects.

Energy store

A way energy is held, such as kinetic or thermal.

Transfer

Energy moving from one store to another.

Dissipated

Spread out to the surroundings in less useful stores.

Closed system

A system where no energy enters or leaves.

Work done

Energy transferred by a force or a current.

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Energy

Lesson 1 of 7

YOUR TASK

Store to Store

10 minutes

For each situation, name the store that decreases and the store that increases. (a) A car braking. (b) A book falling off a shelf. (c) A battery powering a motor lifting a weight. (d) A bow being drawn and released.

1

Name the store before.

2

Name the store after.

WHAT A GOOD ANSWER SHOWS

(a) Kinetic decreases; thermal (brakes) increases. (b) Gravitational potential decreases; kinetic increases. (c) Chemical decreases; gravitational potential increases (plus some thermal). (d) Chemical (archer) to elastic potential, then elastic decreases; kinetic of the arrow increases.

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Can I...?

Energy

Lesson 1 of 7

Name the main energy stores.

Name the four transfer pathways.

Define a system.

Describe energy changes for an object projected upwards.

Describe energy changes when a vehicle slows down.

Describe how a kettle heats water.

Use 'increases' and 'decreases' correctly.

State that total energy is conserved.

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Summary & Exam Focus

Energy can be transferred, stored or dissipated but not created or destroyed.

Describe changes with 'store decreases' and 'store increases'.

Pathways: mechanically, electrically, by heating, by radiation.

In a closed system the total energy does not change.

EXAM FOCUS

A car slows down to a stop using its brakes. Describe the changes in the way energy is stored. (2 marks)

Say which store decreases and which increases.

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