# Heat Transfer Heat Transfer Conduction Convection and Radiation Conduction

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```					         Heat Transfer

Conduction, Convection and Radiation
Conduction
 Conduction – heat
transferred by particles
colliding into one
another, such as in a
metal.
 Transfer of energy by
touch
 Not an effective
transfer in a gas.
 Primarily solids
Convection
 Convection – heat transferred by the circulation
of a fluid (or gas), such as in a heating system at
home; important near the surface of the Sun.

 Hot air rises cool
air falls
 Radiation – heat transferred by the flow of
electromagnetic radiation, like heat felt from the
campfire.
 Radiation is the only type of heat transfer that can
happen in a vacuum.
 Heat transfer through
waves
Heat Transfer
 CONDUCTION: the transfer of energy through matter
by direct contact of particles.
This can happen in solids, liquids and gases.

 CONVECTION: the transfer of energy because of the
movement of bulk masses of
particles.
This can happen only in liquids and gases - not in solids.
 RADIATION:                       the transfer of energy by
electromagnetic waves.
Energy can move by radiation in air like the heat from your electric stove top, or in the
vacuum of space the way the Sun heats the Earth. In radiation, the energy does not have to
transfer through mass (particles).
Heat Vent
Heat Transfer Experiment
From the sun:
I R Scan
Metal Rod
68   In which container is the substance unable to transfer heat by convection?

F                                    H

G                                    J
Air Currents
Heat cells in mantle/asthenosphere
Rising heat cells - plates separate      Sinking heat cells - plates pulled down into mantle
The Sun
heat transfer : Problem 10
Heat convection occurs in gases and
liquids. Heat convection does not occur in
solids because solids are unable to —
A   absorb heat by vibrating
B   transfer heat by fluid motion
C   emit radiation by reflecting light
D   exchange heat by direct contact
Each finger is a different metal rod with glass marbles affixed using
wax. The marbles are placed at equal distances on each of the
rods and the rods are heated. The heat is moved through the metal
to the wax adhesive. As the wax warms up, it looses its stickiness
and the marbles subsequently fall off.
Problem 11
In which container is the
substance unable to
transfer heat by convection?


Problem 12
The moon’s surface becomes hot during the
long lunar day because the sun transfers heat
to the moon. This heat transfer is
accomplished almost entirely through the
process of —
F convection
G refraction
H conduction
Microwave
Problem 13
A man who was sleeping wakes up because he
hears the smoke alarm go off in his house.
Before opening the bedroom door, the man
feels the door to see whether it is warm. He is
assuming that heat would be transferred
through the door by —
A conduction
B convection
D compression
Problem 14
The transfer of heat by the movement of air
currents in Earth’s atmosphere is an
example of —
A   conduction
B   convection
D   fusion
Heat Lamps
Problem 15
A solar heater uses energy from the sun
to heat water. The heater’s panel is
painted black to —

F improve emission of infrared radiation
G reduce the heat loss by convection
currents
H improve absorption of infrared radiation
J reduce the heater’s conducting properties
65 Heat convection occurs in gases and liquids. Heat
convection does not occur in solids because solids are
unable to —

A   absorb heat by vibrating
B   transfer heat by fluid motion
C   emit radiation by reflecting light
D   exchange heat by direct contact
Hot pool near Red Cone Geyser; William S Keller; 1964
66 A solar heater uses energy from the sun to heat
water. The heater’s panel is painted black to —

F   improve emission of infrared radiation
G    reduce the heat loss by convection currents
H    improve absorption of infrared radiation
J   reduce the heater’s conducting properties
56   Which of the following is an example of solar energy being
converted into chemical energy?

F   Plants producing sugar during the day
G    Water evaporating and condensing in the water cycle
H    The sun unevenly heating Earth’s surface
J   Lava erupting from volcanoes for many days
Temperatures of Water in
Different Containers
Initial        Final
Container       Temperature    Temperature
(°C)          (°C)
P             90               83
Q             90               76

69 Container P and Container Q each were filled with 0.5 liter of water. The water
was heated to 90°C. The table shows the temperatures after both containers were
allowed to cool for 3 minutes. Compared to Container Q, Container P is a better —

A    conductor
B    absorber
D    insulator
54   Which process best shows the conversion of solar energy to
chemical energy?

F   Prevailing winds causing windmills to spin
G   Green plants making their own food
H    Uranium producing heat to make steam
J   Tides generating electricity
57     Why is the sum of the products’ energy in this
reaction less than the sum of the reactants’ energy?

A Energy is given off as heat.
B The products absorb available energy.
C Energy is trapped in the reactants.
D The reactants’ energy is less than the melting
point of glucose.
58      An inventor claims to have created an internal
combustion engine that converts 100 kJ of chemical energy
from diesel fuel to 140 kJ of mechanical energy. This claim
violates the law of conservation of —

F   momentum
G   inertia
H    energy
J   mass
Solar Radiation and Earth
Amount of Energy
Effect                                    per Second
(terajoules)
Solar radiation reaching Earth                                   173,410
Radiation reflected back into
52,000
space
81,000
landmasses, and oceans
370
and ocean currents
40
photosynthesis
?
evaporation of water

59          Assuming the chart contains all energy transformations in the Earth
system, how much solar radiation goes toward evaporating water?

F   40,000 terajoules
G    92,410 terajoules
H    121,410 terajoules
J   133,410 terajoules
60 According to the equation E = mc2, mass —

F   travels at the speed of light
G   can be transformed into energy
H   contains light energy
J   is doubled when exposed to light
63 Because ancient Greeks lived close to water, they may have
enjoyed a more constant climate than if they had lived inland. Water
warms up and cools down more slowly than land. This is because of
water’s —

F   boiling point
G   specific heat
H   melting point
J   specific gravity
Temperature      Mass
(°C)           (g)

Metal Block           120          100

Water               20          400

62 The temperature of the water increases by 8°C when the metal
block is added. Which could cause the temperature of the water to         increase
by 10°C after the metal block is added?

F     Using 500 g of water
G     Using a larger beaker
H     Adding more 20°C water
J     Adding heat to the metal block
Q = mcΔt
 Q – Energy (Heat gained or lost)
 m – Mass
 c – Specific Heat
 Δt – Change in Temperature         Q

m   c   Δt
64     How much heat is lost by 2.0 grams of water if the
temperature drops from 31°C to 29°C? The specific heat
of water is 4.184 J/g·°C.

A    4.0 J
B    6.2 J
C    8.4 J
D    16.7 J

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 views: 367 posted: 8/6/2011 language: English pages: 41