energy transfer chapter 9. energy transfer energy is transferred from hotter object to colder object...
TRANSCRIPT
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Energy Transfer
Chapter 9
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Energy Transfer
• Energy is transferred from hotter object to colder object
• Examples?– Cooking pasta– Making ice– Making popcorn– Roasting marshmallows
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Three Methods of Energy Transfer
• Conduction
• Convection
• Radiation
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Conduction• Transfer Energy as heat between particles
in direct contact
• Example– Roasting marshmallow with wire– Air molecules collide with wire
• Transfer energy to wire• Particles in wire move faster, have more E• E then transfer to hand, detect warmth
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Convection
• Energy transfer through movement of fluids at different temperatures (fluids - liquids and gases)
• Examples– Camp fire
• See soot, embers rise & swirl• Rise upwards – warm air expands
– Why?
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Convection
• Convection current – flow of fluid due to heated expansion followed by cooling and contraction
• Examples– Fire, candle
• Warm air rises, cools, then flows downward
– Wind current– Boil water in pot
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Convection
• You can hold your fingers beside the candle flame without harm, but not above the flame. Why?
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Radiation• Transfer of Energy by electromagnetic
waves
• No movement of matter – will work in vacuum or outer space
• No contact or movement of fluid
• Infrared, visible light, UV rays
• Example– Fire emits radiation (infrared), skin absorbs E,
increase in temperature
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Energy Transfer from SunEnergy Transfer from Sun
• Electromagnetic energy is a type of energy that is radiated by the sun in the form of transverse waves vibrating at right angles to the direction of movement
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Radiation occurs in different forms identified by their wavelength
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• WHAT HAPPENS TO ELECTROMAGNETIC ENERGY (RADIATION) ONCE IT REACHES EARTH?
• Radiation is reflected – bounced back at the same angle they arrived
• Radiation is scattered – reflected in various directions
• Radiation is refracted - bent
• Radiation is transmitted – pass through the material
• Radiation is absorbed (taken in as heat energy)
Radiation is reflected – bounced back at the same angle they arrived
Radiation is scattered – reflected in various directions
Radiation is refracted - bent
Radiation is transmitted – pass through the material
Radiation is absorbed (taken in as heat energy)
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Radiation
• Radiation can be absorbed and emitted
• Color– Summer day: wear light or dark clothes?– Winter day: wear light or dark clothes?– Why?