Electrical Energy 0.0 / 5 ? PhysicsElectricityEnergyGCSEAQA Created by: AlexxxFCreated on: 15-03-15 16:47 Electrical Appliances * Electrical appliances can transfer electrical energy into useful energy at the flick of a switch * An electrical appliance is designed for a particular purpose and should waste as little energy as possible 1 of 4 Electrical power * Power is rate of transfer of energy * Unit of power is Watt P=E/t P- Power, W (watts) E- Energy, J (joules) t- time taken for energy to be transferred, s (seconds) Efficiancy = useful power out DIVIDED BY total power in (X 100%) 2 of 4 Using electrical energy * The kilo-watt hour is the enefy supplied to a 1kW appliance in 1 hour. E = P X t E- energy transferred, kWh (kilowatt hours) P- power of the appliance, kW t- time taken for energy to be transferred, hours *Cost of electrical energy Total cost = number of kWh X cost per kWh 3 of 4 Cost effectiveness matters * Cost effectiveness means getting the best value for money * To comparethe cost effectivness of different appliances, we need to take into consideration the number of different costs * Payback time is the time is takes for an appliance or installation to pay for itself in terms of energy savings 4 of 4

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