Transfer of Heat Flashcards
what are conduction, convection & radiation?
why are liquids poor conductors of heat?
3 ways in which thermal energy move from one place to another.
Compared with solids the intermolecular distances in liquids are relatively large & conductive collisions do not occur as often as in solids.
define conduction?
What materials are the best conductors?
Conduction only occurs in solids. T/F?
Mood of transfer of heat by vibrating atoms & free electrons in solids from places of higher temperature to places of lower temperature.
metals
False (gases are the worst conductors.)
Why metals are good conductors as compared to plastic? name others? What are insulators?
because they have free electrons.
woord, cottom, wool, glass, rubber
a material which does not easily allow heat and/or electricity to pass through it.
aka bad conductors
Electrons are the dominant carrier of heat in metals. In metals, the electrons are free to move within a fixed array of positive ions. By colliding, the electrons can transfer heat.
How does the heat flow from hot to cold parts in metals so rapidly than non-metals?
- free electrons move with very high velocities within the metals
- they carry energy at a very fast rate from hot to cold parts as they move.
- Thus, heat reaches the cold parts of the metal object much more quickly than non-metals.
factors that affect the rate of flow of heat?
explain the relation? explain?
cross-sectional area of the solid. Q/t ∝ A
length of the solid. Q/t ∝ 1/L
temperature difference b/w ends.
Q/t ∝ (T1-T2)
FMIGTN
https://energyeducation.ca/wiki/images/5/5c/Crossection.png
What is thermal conductivity? depends on? does it have a symbol or SI unit? formula?
k proportionality constant
Rate of flow of heat across the opposite faces of a metre square of a substance when the temp. difference of 1 Kelvin is maintained across its thickness of 1 meter.
nature of solids.
Q/t x L/A (T1-T2)
(W m-1 K-1)
watt per meter per Kelvin (W/m·K) or W m-1 K-1
define convection?
convection only occur in fluids. T/F
convection currents?
process by which heat is transferred by actual movement of molecules from hot to cold place.
True as particles in solid are in fixed positions.
occur where there is uneven heating of a fluid.
factors affecting rate of radiation emitted/absorbed?
Colour & texture of the surface
Surface temperature
Surface area
Larger the S.A, greater will be the transfer of heat.
explain convection currents pattern?
what causes a glider to remain in air?
As the fluid is heated, its molecules move faster & further apart, which results in the fluid becoming less dense.
The less-dense fluid will then rise, causing denser molecules to fill the space left behind.
the upward movement of air currents help them to stay in air for long period. glider ride over these thermals.
thermals = convection currents
explain land & sea breeze? they are the example of?
sea breeze happens during the day sea to land means cold air from sea to land
land breeze happens during the night
land to sea means cold air from land to sea.
convection
if it is a good emitter, it would be a ____ reflector?
if it is a best absrober, it would be a ____ emitter?
if it is a worst reflector, it would be a ____ emitter?
which color absorbs & reflects the most?
every object is radiating. T/F
radiation can only happen in a vacuum. T/F
bad best best
black white/silver
True
exception: (its temp. is absolute zero)
False it doesn’t require any medium. it can happen through a material too.
every object is radiating = radiations are emitted by all bodies.
why convection is upward?
When the fluid molecules are heated, the fluid becomes larger & lighter. The heated molecules take up more space & rise to the top, while the cooler molecules sink to the bottom. These cooler molecules then become heated.
What is the mechanism of heat transfer from one point to another in conduction?
what happens initially before heating?
The mechanism of heat conduction can be explained by the behavior of atoms within the material.
1. The greater the temp. the more the K.E of atoms & molecules.
2. The atoms in the hotter part of the rod vibrate more violently. Thus possesses more K.E.
The atoms were vibrating about their equilibrium positions.
Explain conduction relating to kinetic molecular description of matter?
define radiation?
mode of transfer of heat from one place to another in the form of waves called electromagnetic waves.
