Physics- P2: Energy Transfer by Heating

What is a conductor?

Materials that allow electrons to move freely inside them

What is an insulator?

Materials that do not have free electrons

What materials make the best conductors?

Metals

What is infrared radiation?

Electromagnetic wave between visible light and

microwaves on the electromagnetic spectrum

What materials make the best insulators?

-Plastic

-Rubber

-Wood

How does conductivity affect the rate of energy transfer?

The greater the thermal conductivity, the more energy/second it transfers by conduction.

How does the thickness of a metal affect the rate of energy transfer through it?

The thicker a metal is, more the time it will take for the heat to get transferred

How does the infrared radiation depend on the temperature?

The higher the temperature, the more infrared radiation emitted

What is the relationship between temperature and absorption/emission of radiation?

Direct proportion

How is the temperature of the earth affected by absorbed/emitted radiation?

-Infrared radiation is reflected from the sun back into space or absorbed by earth’s atmosphere/surface

-It is emitted from the earth’s surface/atmosphere back into space

-This warms the earth

How do greenhouse gases like methane and carbon dioxide use radiation to heat the earth?

-They absorb a longer wavelength infrared radiation from the earth and prevent it escaping into space

-They absorb the radiation and emit it back into the surface

-Making the earth warmer than it would be if these gases were not in the atmosphere

What is black body radiation?

An object that absorbs all the radiation that hits it and does not reflect/transmit any radiation

What is specific heat capacity?

Energy needed to raise the temperature of 1kg of a substance by 1 degree

How can you calculate specific heat capacity?

Energy transferred ÷ mass × temperature change

How can you calculate energy transferred?

mass × specific heat capacity × temperature change

How does the mass of a substance affect how quickly its temperature changes when you heat it?

As the amount of a substance increases the rate of temperature change decreases

How are homes heated?

-Electric/ gas heaters

-Oil/gas central heating systems

-Solid fuel in stoves/fireplaces

How can you reduce the rate of energy transfer from your home?

-Loft insulation

-Cavity wall insulation

-Aluminium foil between radiator/wall

-Double glazed windows

What is cavity wall insulation?

-A space between two layers of brick

-Insulation is pumped into the cavity

-It is a better insulator than the air it replaces

-It traps the air in small pockets, reducing rate of energy transfer by conduction

What is black body radiation?

Radiation emitted by a perfect black body

What is convection?

Circulation of a fluid caused by increasing its thermal energy

What is a fluid

Liquid or gas