Methods of Heat Transfer

A teacher has a large tank of water in which he wants to set up a convection current.

Which of the following arrangements would do this?
1. cooling at X
2. cooling at Y
3. heating at Y
4. heating at Z
One of the following cannot be explained by the movement of molecules.
Which one is it?
1. convection
2. expansion
3. evaporation
4. conduction
The radiators on motor-cars are painted black because ..........................
1. black colour is more beautiful
2. a black surface can conduct heat more better
3. a black body is a good emitter of heat
4. it will not get dirty easily
By which process is thermal energy transffered through a vacuum?
1. radiation only
2. conduction and convection only
3. conduction only
4. convection only
Which types of surface are the best absorbers and the best emitters of infra-red radiation?
1. Best absorber: black & dull ; Best emitter: black & dull
2. Best absorber: black & dull ; Best emitter: white & shiny
3. Best absorber: black & shiny ; Best emitter: white & dull
4. Best absorber: white & dull ; Best emitter: black & shiny
A small cork is attached to a metal plate with wax. An electric heater is placed so close to the plate.
After a time, the wax melts and the cork drops off.

How does the heat reach the cork?
1. By conduction only
2. By convection only
3. By conduction and convection
4. By conduction and radiation
The diagram shows ice cubes being used to lower temperature of a drink.

What is the main process by which the liquid at the bottom of the glass cools?
1. conduction
2. convection
3. radiation
4. a combination of radiation and conduction
The diagram shows a simple form of solar water heater.

Which tubing would give the hottest water from the outlet?
1. black plastic
2. copper painted black
3. copper painted white
4. white plastic
In solids, thermal energy is transffered by conduction.
What is the cause of conduction?
1. Change in density
2. Expansion
3. Infra red radiation
4. Molecular vibrations
Water in the beaker at X as shown.

Which diagram best shows the convection currents?
1. A
2. B
3. C
4. D
A slice of bread is placed under a red hot electric grill to make toast.

How does the heat energy reach the bread?
1. by conduction only
2. conduction and radiation
3. by convection and radiation
4. by radiation only
The diagram shows a crystal being heated in a beaker of water. The crystal released a dye that shows how the water circulates around in the beaker.

What is happening to cause the water above the crystal to rise?
1. The water contracts and its density decreases.
2. The water contracts and its density increases.
3. The water expands and its density decreases.
4. The water expands and its density increases.
In the process of convection, energy is transferred ............................
1. because of density differences in a fluid
2. because of temperature differences in a solid
3. by the diffusion of moleciles throughout a fluid
4. by the vibration of molecules about a mean position
In solids, thermal energy is transferred by conduction.
What is the cause of conduction?
1. change in density
2. expansion
3. Infra red radiation
4. molecular vibrations
Which factors increases the rate of evaporation of a liquid?

increasing its
temperature increasing its
surface area increasing its
depth
A yes yes yes
B yes yes no
C yes no yes
D no yes yes
1. A
2. B
3. C
4. D
The diagram shows a thick copper plate that is very hot. One side is black, the other is shiny. A student places her hands the same distance from each side as shown.
Her left hand feels warmer than her right hand.
Which statement is the correct conclusion from the experiment?
1. The black side is hotter than the shiny one.
2. The black side radiates more heat.
3. The shiny side radiates more heat.
4. The shiny side is cooling down faster than the black side.
A thin plastic blanket, with a shiny metallic surface, is wrapped around a walker who has collapsed after a steep climb.

Which type of heat loss is the shiny surface intended to reduce?
1. conduction
2. convection
3. evaporation
4. radiation
When a liquid evaporates, some molecules escape from it and its temperature is affected.

From where do the molecules escape and what is the effect on the temperature of the liquid?

molecules escape from temperature of liquid
A all parts of the liquid decreases
B all parts of the liquid increases
C only the liquid surface decrease
D only the liquid surface increase
1. A
2. B
3. C
4. D

	increasing its temperature	increasing its surface area	increasing its depth
A	yes	yes	yes
B	yes	yes	no
C	yes	no	yes
D	no	yes	yes

	molecules escape from	temperature of liquid
A	all parts of the liquid	decreases
B	all parts of the liquid	increases
C	only the liquid surface	decrease
D	only the liquid surface	increase

Methods of Heat Transfer

Multiple Choice Questions