One of the topics studied in GCSE Science is the transfer of heat energy This is one of eight quizzes on that particular subject and it looks specifically at how we can increase or decrease the rate of heat transfer via convection, conduction and radiation.
Heat is thermal energy and can be transferred from one location to another by conduction through solids, convection in fluids and as heat rays (thermal radiation). Conduction and convection involve the movement of particles but thermal radiation involves the electromagnetic waves known as infrared. These travel at the same speed as other electromagnetic radiation - the speed of light. This makes radiation the fastest way for heat to move from one place to another. It is so fast that it only takes just over 8 minutes for heat to reach the Earth from the Sun, about 150,000,000 km away!
Conduction is how thermal energy is transferred through solids and the speed at which this happens varies. It is fastest in metals, which are good conductors of heat, and we can use them to increase the rate of heat transfer. Materials that do not allow heat conduction to happen quickly are called insulators. These are things like plastics, wood and materials that contain trapped air or other gases. We can use insulators to decrease the rate of heat transfer.
Convection occurs in fluids and is the reason that hot air rises. A fluid is a liquid or gas. An area of a fluid that is warmer than surrounding areas is less dense and it rises. Cooler fluid then moves in to take its place. If the heating continues, the cooler fluid soon warms up and rises away from the heat source setting up a convection current. When you boil something in a pan, convection is the process that spreads the heat through the liquid.
Finding ways to increase and decrease the rate of thermal energy transfer is important in many applications. A scientist working in the Antarctic or a mountaineer climbing Everest both need clothing that slows down how fast that heat is transferred away from their bodies. Designers of LED lighting systems and computers on the other hand, need to find ways of increasing the rate of heat transfer to cool down the two devices.