3569966
Heat & Its Effects and
Transfer of Thermal
Energy
- Movement of Thermal Energy
- flows from a region of
higher temperature to
a region of lower
temperature
- Thermal energy transfer
- Conduction
- Thermal energy transfer
through a medium or material
from one particle to another
- All matter are conductors of
thermal energy
- Good conductors
- Poor insulators
- Metals
- Solids (fastest
conductor)
- Poor insulators
- Poor conductors
- Good insulators
- Non-metals
- Liquids & Gases
- Good insulators
- Good conductors
- All matter are conductors of
thermal energy
- Thermal energy transfer
through a medium or material
from one particle to another
- Convection
- Thermal energy transfer by movement of
fluids (liquids & gases)
- Happens only in
liquids & gas ( fastest
in gas)
- Expansion of heated
liquids & gas
- Volume increases
- Mass remains the same
- Density decreases
- Convection current
- When a fluid is heated, it expands. It will
become less dense and rises. Cooler fluid,
which is denser, will sink to replace the
warm fluid.
- When a fluid is heated, it expands. It will
become less dense and rises. Cooler fluid,
which is denser, will sink to replace the
warm fluid.
- Volume increases
- Happens only in
liquids & gas ( fastest
in gas)
- Thermal energy transfer by movement of
fluids (liquids & gases)
- Radiation
- Thermal energy transfer in the from of
waves, without a medium
- Happens in all matter & vacuum
- Total surface
area of the body
- Larger surface area
radiates/absorb thermal
energy faster
- Larger surface area
radiates/absorb thermal
energy faster
- Temperature
of the body
- Hotter body radiates faster
- Hotter body radiates faster
- Nature of the
surface of the
body
- Black, rough, dull (good
absorber/radiator)
- White, smooth, shiny (Good reflector)
- Black, rough, dull (good
absorber/radiator)
- Happens in all matter & vacuum
- All objects emit
infra-ray radiation and
all objects absorb it.
- Different objects
emit and absorb
infra-ray radiation
at different rates
- Different objects
emit and absorb
infra-ray radiation
at different rates
- Thermal energy transfer in the from of
waves, without a medium
- Conduction
- flows from a region of
higher temperature to
a region of lower
temperature
- Uses of Expansion & Contraction
- Bimetallic Strips
- Two different
strips riveted or
welded together
- Brass expands/contracts more than Iron when heated
- Two different
strips riveted or
welded together
- Bimetallic Strips
- Expansion & Contraction
- When a matter is heated it
increases in volume and
expands
- When a matter is cooled, it decreases in
volume and contracts
- Fastest in gas, slowest in solids
- When a body expands or contracts, large forces may be set up
- Effects
- Cracking in roads and pavements
- Warping in MRT and railway
- Snapping telephone wires
- Cracked glassware
- Cracked water pipes
- Bridges may damage
- Cracking in roads and pavements
- Solutions
- Expansion gaps (cracks in
road & warped MRT)
- Telephone wires strung loosely
- Pyrex glass (expands
very little when heated)
- Rollers (damaged bridges)
- Expansions bends (water pipes)
- Expansion gaps (cracks in
road & warped MRT)
- Effects
- When a matter is heated it
increases in volume and
expands
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