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Physics

Transfer of Energy

QuestionAnswer
What is Thermal Radiation? Thermal radiation is how heat energy travels by electromagnetic waves.
Radiation travels- Equally in all directions
Every object gives emits thermal radiation- THE HOTTER AN OBJECT IS, THE MORE THERMAL RADIATION IT EMITS.
Thermal radiation(heat radiation) is also known as.. Infra red radiation or IR radiation.
Which device converts thermal radiation to electricity? Thermopile converts thermal radiation to electricity.
What medium does radiation need to travel through? Radiation does not need any medium as it can travel through a vacuum. Gases tend to allow radiation through better than liquids,liquids better than solids.
The transfer of thermal energy through space from the Sun to the Earth is by.. Radiation- It's the only type of heat transfer that can travel through a vacuum. It can travel 300,000km/sec.
Conservation of energy rule... Energy cannot be created or destroyed but can only be transformed from one to another.
Fact The bigger the temperature difference the faster heat is transferred between a body and it's surroundings.
Hot and cool objects an object that's hotter than it's surroundings emits more radiation than it absorbs, as it is cooling down, other way for cooler objects, it absorbs more radiation.
The amount of heat radiated depends on Surface area The bigger the surface area the more waves can be emitted from the surface-so the quicker the transfer of heat.
THE COLOUR OF A SURFACE AFFECTS HOW MUCH RADIATION IT EMITS. Colour-Dark surfaces absorb and emit heat radiation much better than light surfaces such as white.
THE SMOOTHNESS OF A SURFACE AFFECTS HOW MUCH RADIATION IT EMITS. A matt surface(rough) absorbs and emits more radiation than a shiny smooth surface because it has a lot of cavities
CONDUCTION Conduction of heat- occurs mainly in solids
Conduction of Heat CONDUCTION OF HEAT is the process where vibrating particles pass on their EXTRA KINETIC ENERGY to NEIGHBOURING PARTICLES.
and it's because of their free electrons.. Metals conduct so well because the electrons are free to move inside the metal. At the hot end electrons move faster and collide with other free electrons. Free electrons can move freely so this is a faster way of transferring energy through a metal.
The best conductor The best conductor is Copper
Conduction is best at..... Conduction is more efficient through a short fat rod than a long thin rod.It depends on how far the electrons have to travel.
Heat transfer by conduction can be increased by 1.Using a better conducting substance 2.Decreasing the thickness of the substance 3.increasing the area of the substance 4.increasing the temperature difference across the substance.
CONVECTION CONVECTION occurs when the more energetic particles move from the hotter region to the cooler region- AND TAKE THEIR HEAT ENERGY WITH THEM.
CONVECTION CURRENTS Convection occurs in fluids(gases and liquids. CONVECTION CURRENTS are all about CHANGES IN DENSITY.
HEAT TRANSFER Small objects lose heat at a faster rate than large animals. This is because they have a larger surface area compared to their volume.
EXAM TRICK ALWAYS STATE WHICH FOR OF HEAT TRANSFER IS INVOLVED AT ANY POINT.
Created by: angelagana