Energy Transfer by Heating


Specific Heat Capacity

- specific heat capacity of a substance is the amount of energy needed to change the temperature of 1kg of a substance by 1°C

- energy transferred = mass x specific heat capacity x temperature change

- the greater the mass of an object, the more slowly it's temperature increases when it is heated

- the find the specific heat capacity of a substance, use a joulemeter and a thermometer to measure energy transferred for a measured mass, then use:

    specific heat capacity = energy transferred / (mass x temperature change)

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Heating and Insulating building

- electric and/or gas heaters and gas or oil-fired central heating or solid fuel stoves are used to heat houses 

- the rate of energy transfer from houses can be reduced by using:

    loft insulation

    cavity wall unsulation

    doubles glazed windows

    alumnium foil behind raadiators

    external walls with thicker bricks and lower thermal conductivity 

- cavity wall insulation is insulation material that is used to fill the cavity between the two brick layers of an external house wall

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Energy Transfer by Conduction

- metals are best conductors of energy

- non-metal materials such as wool and fibreglass are the best insulators

- the higher the thermal conductivity of a material, the higher the rate of energy transfer through it 

- the thicker the layer of insulating material, the lower the rate of energy transfer through it

- the energy transfer depends on:

    the temperature difference across the material

    the thickness of the material

    the thermal conductivity of the material

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Infrared Radiation

- all ojects emit and absorb infrared radiation, the hotter an object is, the more infrared radiation it emits in a given time

- blackbody radiation is radiation emitted by a body that absorbs all the radiation incident on it

-  it is part of the electromagnetic spectrum, longer in wavelength than visible light waves 

- Earth's atmosphere doesn't block out infrared radiation or light from sun

- the temperature of an object increases if it absorbs more radiation than it emits

- the Earth's temperature depends on a lot of factors, including the absorption of infrared radiation from Sun, and the emission of radiation from the Earth's surface and atmosphere

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