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Revision activity Infra red is another name for thermal radiation A dark surface will absorb radiation better than a light surface Metals are good conductors because they have free electrons Hot Air rises because it is less dense than cold air A radiator has a large surface area so that it can lose heat easily Chemical Energy is the type of energy stored in fuel and food Energy is measured in units of Joules (j) Kinetic energy is the energy of moving object Power = Insulators are materials Energy transferred Time taken that do not conduct heat or electricity very well The National Grid is a network of cables and transformers A Generator is a device for turning kinetic energy into electrical energy Gravitational energy is the energy of an object due to its position Energy cannot be created or destroyed Useful energy is energy transferred to where it is wanted in the form it is wanted are turned by water running downhill Hydroelectricity generators Step up transformers step up power stations’ voltage to grid voltage Geothermal energy comes from the energy released by radioactive rocks deep inside the Earth The efficiency of a device = Useful energy transferred by the device Total energy supplied to the device Electrical energy is energy transferred by an electric current Convection only takes place in liquids and gases Energy Power of device x Time in use transferred = 230 volts is the voltage of mains electricity that we use in the home Burning fossil fuels releases greenhouse gases Heat loss from a building can be stopped by insulating the walls, fitting double glazing and insulating the loft Wasted energy is the energy that is not usefully transferred or transformed The unit of power is The watt (W) A step down transformer steps the voltage down so that it can be used in our homes Uranium is a radioactive metal that can be used in power stations A tidal power station traps water each high tide and uses it to turn generators