Do now!Can you finish the questions

you started last lesson?

Energy transfer (change)

A lamp turns electrical energy into heat and light energy

Sankey Diagram

A Sankey diagram helps to show how much light and heat energy is produced

Sankey Diagram

The thickness of each arrow is drawn to scale to show the amount of energy

Sankey Diagram

Notice that the total amount of energy before is equal to the total amount of energy after (conservation of energy)

Efficiency

Although the total energy out is the same, not all of it is useful.

Efficiency

Efficiency is defined as

Efficiency (%) = useful energy output x 100

total energy input

Example

Efficiency = 75 x 100 = 15%

500

Energy efficient light bulb

Efficiency = 75 x 100 = 75%

100 That’s much better!

More complex examples

You then did some questions!

Thermal energy transfer

Thermal energy transfer

Can you quickly and quietly gather around Mr Porter?

Thermal Energy Transfer

Heat can travel by Conduction

Hot particles vibrate more, so collide with adjacent particles. The heat energy travels from hot to cooler areas.

hot cold

Heat can travel by Conduction

Metals are good conductors of heat

Why?

Heat can travel by Conduction

Metals are good conductors of heatThey have

free electrons that can move from atom to atom carrying

thermal energy too

Heat can travel by Conduction

Most gases are poor conductors of heat (insulators)

Why?

Heat can travel by Conduction

Gases are poor conductors of heat (insulators)

The atoms are too far apart for the vibrations to be passed easily.

Heat can travel by Convection

Heat can travel by Convection

A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed.

Examples of Convection

Heat cannot travel in solids by convection.

Why?

There’s one other way!

¡Uno mas!

Infrared radiation

Infrared radiation

Heat can travel by infrared radiation (“Hot light”!)

Infrared radiation

Infrared radiation can travel through a vacuum (and through air)

Infrared radiation

Black objects are good absorbers of infrared radiation.

Infrared radiation

Shiny objects reflect infrared radiation.

Nottingham Forest winning the champions league in 1979

Infrared radiation

Which would cool fastest?

100°C 100°C

Shiny!

Let’s try!

1. Carefully fill two cans with boiling water.

2. Take their temperature every 5 minutes, filling in the table Mr Porter has just given you.

Whilst you’re doing that you can do a brain map of the previous pages!

Infrared radiation

Black objects are good EMITTERS of IR radiation

100°C 100°C

Shiny!

Brain maps again!

Brain maps again!

• Few words

• Colours

• Pictures

Brain map

Mr Porter will put the Powerpoint on loop. Can you brain-map the information?