P2: Energy transfer by heating Flashcards
What are the three ways to transfer energy by heating
Conduction
Convection
Radiation
What are metals good for
Good thermal conductors
Good conductors of electricity
What is conduction and where does it occur
Conduction occurs mainly in solids
It is the process where vibrating particles transfer energy to neighbouring particles
What happens when we transfer energy to an object by heating
Energy transferred to an object by heating is transferred to the thermal store of that object. This energy is then shared across the kinetic energy stores of the particles of the object
How else can we explain conduction
Particles in part of an object being heated, vibrate more and collide with each other. The collisions cause energy to be transferred between kinetic energy stores.
What is thermal conductivity
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 particles quickly
What is convection and where does it occur
Convection occurs only in liquids and solids.
Convection is when energetic particles move from hotter to colder regions
What happens if we heat a region of gas or liquid
Particles move faster and space between individual particles increase. This causes the density of the heated region to decrease.
Because gases and liquids can flow, the warmer and less dense region will rise above colder, denser regions. if there is a constant heat source, a convection current is creeated.
What is radiation
Radiation creates convection currents and only occurs in gases. 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. The air by the radiator becomes warmer and less dense. The warm air rises and is replaced with cooler air. Cooler air is then heated by the radiator.
At the same time, previously heated air transfers energy to the surroundings (walls and contents of the room). It cools, becomes denser then sinks.
The cycle repeats causing a flow of air to circulate around the room. This is a convection current.
What are the two ways we can reduce energy
Lubrication
Insulation
What is lubrication
Reduces frictional forces.
When something moves, theres normally at least one frictional force acting against it. This lets some energy in the system dissipate.
Eg: Air resistance can transfer energy from a failing object’s kinetic energy store to its thermal energy store.
Objects being rubbed together, lubricants can reduce the friction between the object’s surfaces when they move. Lubricants are usually liquids (eg: oil) so they can flow easily between objects and coat them
What is insulation
Insulation is material designed to prevent heat or sound from being transmitted from one area to another
What can we do to prevent energy losses from heating
Thick walls
Double glazed windows
Draught excluders
Loft insulation
Cavity walls
How can we prevent energy loss from heating
Have thick walls made from a material with a low thermal conductivity. The thicker the walls and the lower the thermal conductivity, the slower the rate of energy transfer will be so the building will cool slowly
What are draught excluders
Draught excluders are located around doors and windows, and reduce energy transfer by convection
