Energy transfer by electromagnetic waves
Q. Dark, Matt surfaces...
emit more infrared radiation than light, shiny surfaces.
they also absorb more infrared radiation than light, shiny surfaces.
fixed shape and volume
fixed volume but no shape
does not have a fixed volume and can flow
What are the best insulators?
Wool and fibreglass
Why are non-metals poor conductors?
they do not contain free electrons
What is convection?
Convection is the circulation of a fluid (liquid or gas) caused by heating it.
Convection takes place in only liquids and gases.
What is evaporation?
Evaporation is when a liquid turns into a gas.
What is condensation?
Condensation is when a gas turns into a liquid.
How could you increase evaporation?
-Increasing the surface area of the liquid
-Increasing the liquid's temperature
-Creating aa draught of air across the liquid's surface
How could you increase condensation on a surface?
-Increase the area of the surface
-Reduce the temperature of the surface
What does the rate of energy transferred to or from an object depend on?
-The shape size and type of material of the object.
-The materials the object is in contact with.
-The temperature difference between the object and it's surroundings.
Energy transfer equation
Energy transferred in joules (J)=mass in kilograms (kg) x specific heat capacity J/kg °C x temperature in degrees celcius (°C)
E= m x c x θ
Rearrange the previous equation to find the specific heat capacity of something
c = E ÷ m x θ
Q. The greater the mass of an object...
The more slowly it's temperature increases when it is heated
What does the rate of temperature change of a substance when it is heated depend on?
-The energy supplied to it
-it's specific heat capacity
U-values tell us how much energy per second passes through different materials
Q. The lower the U-value...
the more effective the material is as an insulator.
How can energy transfer from our homes be reduced?
-Cavity wall insulation
-Aluminium foil behind radiators
Q. Cavity wall insulation reduces the rate of energy transfer due to...
Q. Aluminium foil behind a radiator reduces the rate of energy transfer due to...
Q. Closing the curtains in the winter reduces the rate of energy transfer due to
Convection and Radiation