Physics 1 Revision

Lesson 3

Energy transfer and efficiency

Energy transfer and efficiency

Energy cant be created or destroyed, it just turns into another form

Energy transfer diagrams show input, useful and wasted energy

Wasted energy is usually heat & sound. This energy goes into the surroundings

Chemical kinetic (useful)sound (wasted)heat (wasted)

An appliance that wastes les energy is called

energy efficient

Efficiency = useful energy / total energy

Energy efficient appliances can save you money

Energy is measured in Joules (J)

Sankey diagrams

are a way to show energy efficiency

The thicker the arrow , the more energy input/

output

100 Jelectrical

energy(input)

20 Jelectrical

energy(input)

10 Jlightenergy(output)10 J

heat energy(wasted)

90 Jheat energy(wasted)

10 Jlightenergy(output)

Energy efficient light bulb

Filament light bulb

How long it takes to recover the costs of an

appliance is called pay back time

If loft insulation costs £200 to install and saves you £50 a year in heating bills… the pay back

time is 4 years Ways to make a home

energy efficient

Energy saving light bulbs

Cavity wall insulation

Loft insulation

Draft excluders

Double glazing

The cavity wall insulation in a house costs £6000 to install. It has a payback time of 15 years. How much money does the insulation

save each year in fuel costs?

The double-glazing for a house costs £3,000 but saves £150 per year in fuel costs. What is its

payback time?

Transferring electrical energy

Electrical energy is measured in kW/h

Electrical energy = power (kW) x time (h)

The longer you use an appliance for the more

electrical energy it will transfer

Electricity costs money

The electricity company charges you for every

unit you use

1 unit = 1 kW/h

Example:How much would 10 units

of electricity cost at a price of 9p per unit?

cost =

number of units x cost

per unit

Key words and statements

Joules

Pay back time

Electrical energy transfer

Unit of electricity

Wasted energy

Energy efficiency

Input energy

Useful energy

The unit is kW/h.The amount of energy in joules that is

transferred into the right type of energy

Number of joules that enters the device

Is equal to 1kW/hElectrical companies charge consumers by

units

The time it takes to recover the cost of an energy efficient appliance before you can start

saving money

The amount of energy in joules that is transferred into the wrong type of energy

The amount of electrical energy used and can be measured by power (kW) x time (h)

How well a device transforms input energy into useful energy

The unit for energy

Energy transfer and efficiency

Joules

Pay back time

Electrical energy transfer

Unit of electricity

Wasted energy

Energy efficiency

Input energy

Useful energy

The amount of energy in joules that is transferred into the right type of energy

Number of joules that enters the device

Is equal to 1kW/hElectrical companies charge consumers by

units

The time it takes to recover the cost of an energy efficient appliance before you can start

saving money

The amount of energy in joules that is transferred into the wrong type of energy

Is measured in kW/hThe amount of electrical energy used and can

be measured by power (kW) x time (h)

How well a device transforms input energy into useful energy

The unit for energy

Energy transfer and efficiency

Energy efficient devices usually coast money to install…

The longer an appliance is used for…

The cost of using an appliance will increase when…

If solar panels cosy £2000 pounds to install and it saves £250 pounds in electricity bills

per year…

An energy efficient device…

A Sankey diagram…

Energy cannot be…

Wasted energy is usually…

You use the appliance for longer and when the appliance uses a greater amount of power

It will take 8 years to pay back the cost

Created or destroyed

Is a graph showing input, useful and wasted joules

Heat or sound and goes into the surroundings

The more electrical energy it will transfer

Turns more of it’s input energy into useful energy and wastes less energy

But will save money in the long term. The time is takes to recover the cost of the device is

called pay back time

Energy transfer and efficiency

Energy efficient devices usually cost money to install…

The longer an appliance is used for…

The cost of using an appliance will increase when…

If solar panels cosy £2000 pounds to install and it saves £250 pounds in electricity bills

per year…

An energy efficient device…

A Sankey diagram…

Energy cannot be…

Wasted energy is usually…

You use the appliance for longer and when the appliance uses a greater amount of power

It will take 8 years to pay back the cost

Created or destroyed

Is a graph showing input, useful and wasted joules

Heat or sound and goes into the surroundings

The more electrical energy it will transfer

Turns more of it’s input energy into useful energy and wastes less energy

But will save money in the long term. The time is takes to recover the cost of the device is

called pay back time

Energy transfer and efficiency