Physics-Energy transfer by heating

Energy transfer by heating

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Energy transfer by heating

Infrared radiation

  • Infrared radiation is energy transfer by electromagnetic
  • All objects emit infrared radiation
  • The hotter an object is the more infrared radiation it emits in a given time
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Energy transfer by heating

Surface and radiation 

  • Dark, matt surfaces emit infrared radiation more quickly than light, shiny surfaces
  • Dark, matt surfaces absorb infrared radiation more quickly than light, shiny surfaces
  • Light shiny surfaces reflect more infrared radiation than dark, matt surfaces
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Energy transfer by heating

States of matter

  • Flow, shape, volume and density are the properties used to describe each state of matter
  • The particles in a solid are held next to each other, vibrating in their fixed positions
  • The particles in a liquid move about at random and are in contact with each other
  • The particels in a gas move about randomly and are mich farther apart than particles in a solid or liquid
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Energy transfer by heating

Conduction 

  • Metals are the best conductors
  • Materials such as wool, and fibreglass are good insulators
  • Conduction in a metal is mainly due to free electrons transferring energy inside  the metal 
  • Non-metal are conductors because they do not contain fee electrons
  • Poor conductors are called insulators
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Energy transfer by heating

Convection

  • Convection is the circulation of a fluid (liquid or gas) caused by heating it
  • Convection takes place only in liquids and gases (fluids)
  • Heating a liquid or a gas makes it less dense so it rises and causes circulation 
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Energy transfer by heating

Evaporation and condensation

  • Evaporation is when a liquid turns into a gas
  • Condensation is when a gas turns into a liquid
  • The rate of evaporation is increased by:
  • Increasing the surface area of the liquid
  • Increasing the temperature of the liquid
  • Creating a draught of air across the liquid's surface
  • The rate of condensation is increades by:
  • Increasing the surface area
  • Reducing the surface temperature
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Energy transfer by heating

Energy transfer by design

  • The rate if energy transfer to or from an object depends on:
  • The shape, size and type of materials of the object 
  • The materials the object is in contact with
  • The temperature difference between the object and its surroundings
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Energy transfer by heating

Specific heat capacity

  • The greater the mass of an object, the more slowly its temperature increases when it is heated
  • The rate of temperature change in a substance when heated depends on the energy transferred to it, its mass and its specific heat capacity
  • The equation for specific heat capacity is: E=m x c x o
  • Where:
  • E is energy transferred, J
  • m is mass, kg
  • c is specific heat capacity, J/kg degrees
  • o is temperature change, degrees
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Energy transfer by heating

Heating and insulating bulidings

  • The rate of energy transfer to or from our homes can be reduced
  • U-values tell us how much energy per second passes throguh different materials. The lower the U-value the better the material is as an insulator
  • Solor heating panels do not use fuel to heat water but they are expensive to buy and install
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