physics (2)
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- Created by: Ellie
- Created on: 30-05-14 17:52
what is the dictionary definition of convection current?
the way in which heat energy is transferred through liquids and gases by movement of the particles in the liquid or gas
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can convection happen in solids?
no - only in liquids and gases
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what does the movement of warm and cold gases or liquids create?
a convection current
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explain the process of convection in terms of heat energy - use warm ground and air as an example
The rising of warm air through colder air is called convection. Warm sports on the ground heat the air above, this warm air rises. Colder air falls towards the ground where it is heated. This movement of warm and cool air creates a convection current
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why does water become less dense as it expands?
because the particles are moving faster and move further away
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name 2 household objects that use convection current to make it work
kettle and fridge
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why are gases poor conductors of heat?
because their particles are so spread out
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if you heated a liquid in a test-tube at the top - what would happen?
only the liquid at the top would boil
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are gases and liquids usually conductor or insulators? Explain why in terms of how particles pass of heat energy.
insulators - because their particles are spread apart and for heat to pass the particles have to bump into each other, but as a result of the particles being spread apart, it takes more energy to heat them and the heat can't be transfered as easily
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what is the dictionary definition of infrared radiation?
the way that heat energy is transferred from a hotter place to a colder one
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do all objects give out thermal infrared radiation?
yes - but hotter objects give out more
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does infrared radiation need particles to transfer heat energy from one place to another?
No
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are shiny, light (white) surfaces good at reflecting infrared radiation?
yes, they reflect the radiation
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do shiny, light (white) surfaces give out infrared radiation?
No - they reflect it away. Dark coloured objects are good at giving out, or emitting, heat radiation
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are black or dull surfaces good or poor at absorbing infrared radiation?
They absorb radiation very well - winter coats are often dark and dull as they absorb any slight warmth from the sun. Light-coloured shiny surfaces are bad at absorbing it, they reflect it away
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what do sankey diagrams show?
all the energy transfers taking place in process
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what does a thicker arrow in a sankey diagram symbolise?
the thicker the arrow, the greater amount of energy transferred
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what are 3 examples of ways to conserve energy?
(1) put your central heating on a timer (2) extra layers - put on a jacket etc. instead of putting on the heating (3) have a shorter shower
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how do most heat transfers happen?
by conduction, convection and radiation - often all three
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is infrared wave?
Yes - like light
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what 3 things determine the amount of energy needed to heat a substance?
(1)How much is being heated (2)What it is made of (3)The temperature you want it to be
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why are there often warm air currents over motorways?
because the wheels against the motorway cause friction against the road, and friction uses kinetic energy - and the waste product of kinetic energy is heat. Also the exhaust fumes rise up and heat the motorway
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what is infrared emission?
the emission of heat from infrared waves - matt, dark surfaces are good at emitting heat radiation
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what is infrared absorption?
the absorption of infrared waves - dark, dull surfaces are also good at absorbing radiation
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what is a thermogram?
a record of the image made by a thermal imaging camera (the image made)
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how can a thermal imaging camera produce images in the dark?
It detects the heat that is around as all hot objects give off infrared radiation and the thermal imaging cameras can detect infrared radiation
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identify the colour coded temperature scale on a thermogram
dark blue (coldest), through red to white (warmest)
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explain the process of convection in terms of heat energy, density and movement of regions of the liquid or gas
*
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explain which methods you could use to reduce heat loss from an object
*
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what is the dictionary definition of a sankey diagram?
a scale diagram that shows all the energy transfers taking place in a process
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what is the formula for efficiency (in a sankey diagram)?
*
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what is the formula for energy transferred (in a sankey diagram)?
energy transferred = power x time
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Other cards in this set
Card 2
Front
can convection happen in solids?
Back
no - only in liquids and gases
Card 3
Front
what does the movement of warm and cold gases or liquids create?
Back
Card 4
Front
explain the process of convection in terms of heat energy - use warm ground and air as an example
Back
Card 5
Front
why does water become less dense as it expands?
Back
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