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Reducing energy losses in homes is essential for comfort. ### Heating Methods - Conduction: Energy transfer through vibrations in solids. - Convection: Movement of particles in liquids/gases from hot to cool areas. ### Thermal Conductivity - Measures how quickly energy is transferred through a material. High thermal conductivity means rapid energy transfer. ### Insulation Techniques - Loft insulation: Reduces convection by trapping air. - Cavity walls: Air gaps reduce conduction, while foam insulation cuts convection. - Draught excluders: Minimize convection around windows/doors. - Double-glazed windows: Air gaps reduce conduction. - Thick walls: Slow energy transfer with low thermal conductivity. ### Efficiency of Energy Use - Efficiency: Ratio of useful energy output to total energy input. ext{Efficiency} = rac{ ext{Useful Output Energy}}{ ext{Total Input Energy}} Example: A blender with 70% efficiency using 600 W gives useful output of 0.7 imes 600 = 420 W. No device is 100% efficient. ### Energy Resources - Non-Renewable: Coal, oil, natural gas (finite, abundant, with environmental harm). - Renewable: Solar, wind, etc. (replenishable, sustainable, but weather-dependent). ### Applications - Transport: Oil fuels and biofuels. Heating: Mainly natural gas in the UK, also from coal, bio-fuels, and other sources.