Conduction & Convection

• Conduction occurs mainly in solids
• Conduction is the process where vibrating particles transfer energy to neighbouring particles
• CD - 1. Energy transferred to an object by heating is transferred to the thermal store of the object. This energy is shared across the kinetic energy stored of the particles in the object
• CD - 2. The particles in the part of the object being heated vibrate more and collide with each other. These collisions cause energy to be transferred between particles' kinetic energy stores. This is conduction
• 3. This process continues throughout the object until the energy is transferred to the other side of the object. It's then usually transferred to the thermal energy store of the surroundings (or anything else touching the object)
• 4. Thermal conductivity is a measure of how quickly energy is transferred through a material in this way. Materials with a high thermal conductivity transfer energy between their particles quickly
• Convection occurs only in liquids and gases
• Convection is where energetic particles move away from hotter to cooler regions
• In convection, energy is transferred by heating to the thermal store of the liquid or gas. This energy is shared across the kinetic energy stores of the gas or liquid's particles
• CV - Unlike in solids, the particles in liquids and gases are able to move. When you heat a region of a gas or liquid, the particles move faster and the space between individual particles increases. This causes the density of the region being heated to decrease
• CV - Because liquids and gases can flow, the warmer and less dense region will rise above denser, cooler regions. If there's a constant heat source, a convection current can be created
• Radiators create convection currents
• Radiators - Heating a room with a radiator relies on creating convection currents in the air of the room. Energy is transferred from the radiator to the nearby air particles by conduction (air particles collide with the radiator suface)
• Radiators - The air by the radiator becomes warmer and less dense (as the particles move quicker). This warm air rises and is replaced by cooler air. The cooler air is then heated by the radiator
• Radiators - At the same time, the previously heated air transfers energy to the surroundings (e.g walls and contents of the room). It cools, becomes denser and sinks.
• The cycle in the radiator repeats, causing a flow of air to circulate around the room - this is a convection current