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 J electrical energy (input) 20 J electrical energy (input) 10 J light energy (output) 10 J heat energy (wasted) 90 J heat energy (wasted) 10 J light energy (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/h Electrical 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/h Electrical 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/h 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

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