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Description
Flashcards by Farha Idrees, updated more than 1 year ago
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Created by Farha Idrees
over 6 years ago
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| Question | Answer |
| Which materials are the best conductors of energy? | metals |
| Which materials make the best insulators? | non-metal materials, such as fibreglass and wool |
| define thermal conductivity | the measure of the ability of a material to conduct heat |
| How does the thermal conductivity of a material affect the rate of energy transfer through it by conduction? | the higher the thermal conductivity of a material the higher the rate of energy transfer |
| What does the energy transfer per second through a layer of insulating material depend on? | • the temperature difference • thickness of the material • thermal conductivity |
| How do you reduce the energy transfer as much as possible? | 1. the thermal conductivity should be as low as possible 2. thickness of the insulating layer should be as thick as possible |
| How does the thickness of a layer of material affect the rate of energy transfer by conduction through it? | the thicker the insulating material, the lower the rate of energy transfer through it |
| What is conduction? | the transfer of energy from one atom to another atom |
| Explain how conduction works. | 1. if heat energy is supplied to one part of the solid, the atoms vibrate faster 2. as they vibrate and as the atoms are bonded together, the vibrations are passed on 3. eventually the energy spreads throughout the solid and the overall temperature has increased |
| Why is conduction faster in metals? | the free electrons carry the heat energy transfer and collide with other electrons and atoms |
| What is convection? | the movement of heat in fluids |
| Explain how convection works. | 1. the heater warms the air next to it, which becomes less dense and rises 2. the ceiling forces this air to circulate, therefore warming the air around it 3. when the air has cooled, it falls, completing the cycle |
| What is a convection current and give examples. | a current in a fluid as a result of convection: • water in kettles • soup in saucepans • water in a hot water tank |
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