Heat transfer and waves
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1.Which of the following is the definition of heat conduction?
Easy- ATransfer of energy by electromagnetic waves
- BTransfer of energy through bulk fluid motion
- CDirect microscopic exchange of kinetic energy between particles in physical contact
- DTransfer of energy by phase changes
2.Heat transfer by convection can occur in a vacuum.
EasyTrue or false?
3.Which mechanism of heat transfer does not require a medium?
Easy- AConduction
- BConvection
- CRadiation
- DAdvection
4.Which of the following is an example of forced convection?
Easy- AA hot air balloon rising
- BWater boiling in a pot
- CA fan blowing air over a hot surface
- DHeat from the Sun reaching Earth
5.Which of the following are modes of heat transfer? (Select all that apply.)
Easy- AConduction
- BConvection
- CRadiation
- DReflection
- EAdvection
6.Arrange the following heat transfer mechanisms in order of increasing dependence on a material medium (least to most).
Medium- Radiation
- Conduction
- Convection
7.Match each term with its correct description.
Medium- Thermal equilibrium
- Heat flux
- Enthalpy
- Sum of internal energy plus pressure-volume product
- State when two systems reach the same temperature
- Heat flow per unit area per unit time
8.Heat transfer is a state function, meaning it depends only on the initial and final states of a system.
MediumTrue or false?
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9.Match each mode of heat transfer with its primary mechanism.
Easy- Conduction
- Convection
- Radiation
- Transfer by direct particle collisions
- Transfer by bulk fluid motion
- Transfer by electromagnetic waves
10.Arrange the following heat transfer mechanisms in order of increasing reliance on a material medium (least to most).
Medium- Radiation
- Convection
- Conduction
11.Which of the following are examples of forced convection? (Select all that apply.)
Medium- AA fan blowing air over a hot surface
- BHot air rising from a radiator
- CA pump circulating water in a cooling system
- DA spoon heating up in hot soup
- EWind caused by atmospheric pressure differences
12.Thermal radiation requires a material medium to travel.
EasyTrue or false?
13.Which of the following best describes heat conduction in a metal rod?
Medium- AFree electrons transfer kinetic energy through the metal.
- BThe rod expands and pushes heat along its length.
- CHot fluid rises and cold fluid sinks within the rod.
- DInfrared radiation is emitted and absorbed along the rod.
14.Match each term with its correct definition.
Medium- Heat flux
- Thermal conductivity
- Heat transfer coefficient
- Heat flow per unit area
- Material property to conduct heat
- Proportionality between heat flux and temperature difference
15.Arrange the following substances in order of increasing thermal conductivity (lowest to highest).
Easy- Air
- Water
- Copper
16.A student claims that heat transfer by convection can occur in a vacuum. Is this statement correct?
Medium- AYes, because convection involves fluid motion, and vacuums contain gas particles.
- BNo, because convection requires a fluid medium, and a vacuum has no particles.
- CYes, because radiation is a form of convection.
- DNo, because convection only occurs in solids.
17.Which of the following correctly describes heat transfer by advection?
Medium- ATransfer of energy by electromagnetic waves
- BTransfer of energy by bulk motion of a fluid carrying thermal energy
- CTransfer of energy through direct particle collisions in a solid
- DTransfer of energy by buoyancy-driven fluid motion without external force
18.Heat transfer always occurs from a region of higher temperature to a region of lower temperature, according to the second law of thermodynamics.
EasyTrue or false?
19.A metal rod is heated at one end. Which two mechanisms are primarily responsible for heat transfer along the rod?
Medium- AConduction and radiation
- BConvection and radiation
- CConduction and advection
- DConvection and advection
20.Match each heat transfer mechanism with its primary medium requirement.
Easy- Conduction
- Convection
- Radiation
- Solid or fluid (direct contact)
- Fluid (liquid or gas)
- No medium required (vacuum)
21.In an experiment to investigate thermal conduction along a metal rod, one end of the rod is heated and the temperature is measured at different points along the rod. Which of the following best explains why the temperature decreases with distance from the heated end?
Medium- AHeat is lost to the surroundings by convection and radiation as it travels along the rod.
- BThe thermal conductivity of the rod decreases with distance.
- CThe particles at the heated end vibrate more slowly as heat is conducted.
- DHeat is transferred by convection within the rod.
22.A student is designing an experiment to compare the thermal conductivity of different materials. Which of the following experimental design features are important to ensure a fair test? (Select all that apply.)
Medium- AUsing rods of the same length and cross-sectional area.
- BHeating all rods to the same temperature at one end.
- CMeasuring the temperature at the same distance from the heated end for each rod.
- DUsing rods made of the same material.
- EAllowing the same amount of time for heat to travel.
23.In an experiment to observe convection currents in water, heating the water from below causes the water at the bottom to become less dense and rise, while cooler water sinks.
EasyTrue or false?
24.In a laboratory experiment, a student measures the temperature of a metal block as it cools in air. The temperature decreases rapidly at first and then more slowly. Which of the following best explains this observation?
Medium- AThe rate of heat loss by convection and radiation depends on the temperature difference between the block and the surroundings.
- BThe block's specific heat capacity increases as it cools.
- CThe air around the block becomes a better conductor as the block cools.
- DThe block loses heat by conduction to the air, which becomes less effective over time.
25.Which of the following best defines heat transfer?
Easy- AThe energy exchanged between materials as a result of a temperature difference
- BThe transfer of energy by electromagnetic waves only
- CThe movement of particles in a vacuum
- DThe change in state of a substance
26.Which of the following is NOT a mode of heat transfer?
Easy- AConduction
- BConvection
- CRadiation
- DEvaporation
27.Match each mode of heat transfer with its correct description.
Easy- Conduction
- Convection
- Radiation
- Transfer by bulk fluid motion
- Transfer by direct contact between particles
- Transfer by electromagnetic waves
28.Which of the following are examples of natural convection? (Select all that apply.)
Medium- AA radiator heating a room
- BA hair dryer blowing hot air
- CA hot air balloon rising
- DA fan cooling a computer processor
29.Which of the following best describes thermal conduction?
Easy- ATransfer of heat by bulk fluid motion
- BDirect microscopic exchange of kinetic energy between particles in contact
- CTransfer of energy by electromagnetic waves
- DTransfer of heat through a vacuum
30.A metal rod is heated at one end. After some time, the other end becomes hot. Which two mechanisms are primarily responsible for heat transfer along the rod?
Medium- AConduction and radiation
- BConvection and radiation
- CConduction and convection
- DAdvection and radiation
31.Arrange the following substances in order of increasing thermal conductivity (lowest to highest):
Medium- Air
- Water
- Copper
- Glass
32.In an experiment to investigate thermal conduction along a metal rod, one end of the rod is heated and the temperature is measured at different points along the rod. Which of the following graphs best represents the temperature distribution along the rod at steady state?
Medium- AA horizontal line (constant temperature)
- BA straight line decreasing linearly from the hot end to the cold end
- CAn exponential decay curve
- DA curve that increases then decreases
33.In an experiment to compare thermal conductivity of different metals, identical rods of copper, aluminium, and iron are heated at one end with the same heat source. Which additional measurement would allow the most accurate comparison of their thermal conductivities?
Medium- AMeasuring the time taken for the far end to reach a fixed temperature
- BMeasuring the mass of each rod
- CMeasuring the colour of the rods
- DMeasuring the length of each rod
34.A student sets up an experiment to observe convection in water. A beaker of water is heated from below using a Bunsen burner. Which of the following would be the best way to visualise the convection currents?
Medium- AAdding a few drops of ink to the water
- BPlacing a thermometer at the top of the water
- CMeasuring the time for the water to boil
- DStirring the water with a glass rod
35.In an experiment to measure the thermal conductivity of a metal bar, a student heats one end and measures the temperature at several points along the bar at steady state. Which of the following conditions must be met for Fourier's law to be valid? (Select all that apply.)
Hard- AThe heat flow is one-dimensional along the bar.
- BThe bar is perfectly insulated along its sides.
- CThe temperature gradient is constant along the bar.
- DThe bar is made of a material with variable thermal conductivity.
- EThe heat source maintains a constant temperature at the hot end.
36.Thermal radiation can be transferred through a vacuum.
EasyTrue or false?
37.Match each heat transfer mechanism with the correct description of how it is typically investigated experimentally.
Medium- Conduction
- Convection
- Radiation
- Using a heat source and measuring temperature gradient along a solid bar
- Heating a fluid from below and observing the motion of a dye
- Using a thermopile or infrared camera to detect emitted energy
38.A student performs an experiment to determine the thermal conductivity of a metal rod. Arrange the following steps in the correct order.
Medium- Measure the cross-sectional area and length of the rod.
- Attach temperature sensors at regular intervals along the rod.
- Insulate the sides of the rod to minimise heat loss.
- Heat one end of the rod with a constant heat source.
- Record the temperatures at each sensor after steady state is reached.
- Use Fourier's law to calculate the thermal conductivity from the temperature gradient and heat input.
39.Which of the following is the best example of forced convection?
Easy- AA fan blowing air over a hot computer processor
- BHot air rising from a radiator
- CHeat travelling along a metal rod
- DThe Sun warming the Earth
40.In a convection experiment, heating a fluid from above is more effective at creating convection currents than heating from below.
MediumTrue or false?
41.Complete the sentence about heat transfer.
EasyHeat always flows spontaneously from a region of ____ temperature to a region of ____ temperature.
42.If heat flux is 500 W/m², density is 1.2 kg/m³, specific heat capacity is 1000 J/(kg·K), and velocity is 2 m/s, calculate the temperature difference (in K) using the advection formula φq = v ρ cp ΔT.
Medium43.What is the SI unit of heat transfer (energy) used in the source?
Easy44.A fluid with density 1.2 kg/m³ and specific heat capacity 1000 J/(kg·K) flows at 2 m/s. If the heat flux due to advection is 500 W/m², calculate the temperature difference (in K).
Medium45.Complete the sentence.
EasyThe three modes of heat transfer are ____, ____, and ____.
46.What term describes the property of a material that measures how well it conducts heat?
Easy47.If heat flux is 500 W/m², density is 1.2 kg/m³, specific heat capacity is 1000 J/(kg·K), and velocity is 2 m/s, calculate the temperature difference (in K) using the advection formula.
Medium48.Complete the sentence using the correct term.
EasyThe transfer of heat by the bulk movement of a fluid is called ____.
49.A fluid with density 1.2 kg/m³ and specific heat capacity 1000 J/(kg·K) flows with velocity 2 m/s. If the heat flux due to advection is 500 W/m², calculate the temperature difference in K.
Medium50.A metal rod of length 0.5 m and cross-sectional area 0.01 m² has a temperature difference of 100 K between its ends. If the thermal conductivity of the metal is 200 W/(m·K), calculate the rate of heat transfer (in watts) through the rod by conduction.
Medium51.Name the three modes of heat transfer mentioned in the source.
Easy52.A surface emits thermal radiation with an emissivity of 0.8 and an area of 2 m². If its temperature is 500 K, calculate the power radiated (in watts). Use Stefan-Boltzmann constant σ = 5.67 × 10⁻⁸ W/(m²·K⁴).
Medium53.Explain why a metal spoon left in a hot soup becomes hot, while the handle of a wooden spoon remains cool. Use the particle model of conduction.
Medium54.A student claims that heat transfer by convection can occur in a vacuum. Is this statement correct? Explain your reasoning.
Easy55.If heat flux is 500 W/m², density is 1.2 kg/m³, specific heat capacity is 1000 J/(kg·K), and velocity is 2 m/s, calculate the temperature difference (in K) using the advection formula φq = v ρ cp ΔT.
Medium- A1.2083 K
- B0.2083 K
- C2.2083 K
- D-0.7917 K
56.A fluid with density 1.2 kg/m³ and specific heat capacity 1000 J/(kg·K) flows at 2 m/s. If the heat flux due to advection is 500 W/m², calculate the temperature difference (in K).
Medium- A0.2083 K
- B1.2083 K
- C2.2083 K
- D-0.7917 K
57.If heat flux is 500 W/m², density is 1.2 kg/m³, specific heat capacity is 1000 J/(kg·K), and velocity is 2 m/s, calculate the temperature difference (in K) using the advection formula.
Medium- A1.2083 K
- B-0.7917 K
- C2.2083 K
- D0.2083 K
58.A fluid with density 1.2 kg/m³ and specific heat capacity 1000 J/(kg·K) flows with velocity 2 m/s. If the heat flux due to advection is 500 W/m², calculate the temperature difference in K.
Medium- A0.2083 K
- B2.2083 K
- C1.2083 K
- D-0.7917 K
59.A metal rod of length 0.5 m and cross-sectional area 0.01 m² has a temperature difference of 100 K between its ends. If the thermal conductivity of the metal is 200 W/(m·K), calculate the rate of heat transfer (in watts) through the rod by conduction.
Medium- A400 W
- B480 W
- C360 W
- D440 W
60.A surface emits thermal radiation with an emissivity of 0.8 and an area of 2 m². If its temperature is 500 K, calculate the power radiated (in watts). Use Stefan-Boltzmann constant σ = 5.67 × 10⁻⁸ W/(m²·K⁴).
Medium- A5103 W
- B6237 W
- C5670 W
- D6804 W
Flashcards
What is heat transfer?
Heat transfer is the energy exchanged between materials (solid/liquid/gas) as a result of a temperature difference.
What are the three main mechanisms of heat transfer?
Conduction, convection, and radiation.
Define thermal conduction.
Thermal conduction is the transfer of energy between objects that are in physical contact, via direct microscopic exchanges of kinetic energy of particles.
Define thermal convection.
Thermal convection is the transfer of energy between an object and its environment due to fluid motion (bulk flow of a gas or liquid).
Define thermal radiation.
Thermal radiation is the transfer of energy by the emission of electromagnetic radiation (photons) through a vacuum or transparent medium.
What is advection in heat transfer?
Advection is the transport mechanism of a fluid from one location to another, moving thermal energy by the physical transfer of a hot or cold object.
What is the second law of thermodynamics in relation to heat transfer?
Spontaneous heat transfer always occurs from a region of high temperature to a region of lower temperature until thermal equilibrium is reached.
What is thermal equilibrium?
Thermal equilibrium is when two systems in contact reach the same temperature and no net heat flows between them.
What is the particle model explanation for conduction?
In conduction, particles with higher kinetic energy (hotter) collide with neighbouring particles, transferring energy through the material without bulk movement.
What is natural convection?
Natural convection is fluid motion caused by buoyancy forces when thermal energy expands the fluid (e.g., a fire plume), influencing its own transfer.
What is forced convection?
Forced convection is when fluid is forced to flow by a pump, fan, or other mechanical means to enhance heat transfer.
What is heat flux?
Heat flux is a quantitative, vectorial representation of heat flow through a surface, measured in W/m².
What is thermal conductivity?
Thermal conductivity is the property of a material to conduct heat, evaluated primarily in terms of Fourier's law for heat conduction.
What is the difference between heat and temperature?
Heat is thermal energy transferred due to a temperature difference; temperature is a measure of the average kinetic energy of particles.
What is the unit of heat?
The joule (J) is the unit to quantify energy, work, or the amount of heat.
What is enthalpy?
Enthalpy (H) is a thermodynamic potential equal to the internal energy (U) plus the product of pressure (P) and volume (V).
What is the heat transfer coefficient?
The heat transfer coefficient is the proportionality between heat flux and the thermodynamic driving force for the flow of heat.
How does sound transfer energy?
Sound transfers energy as mechanical waves (longitudinal waves) through a medium by particle vibrations.
How does light transfer energy?
Light transfers energy as electromagnetic waves (photons) and can travel through a vacuum.
What is evaporative cooling?
Evaporative cooling is heat transfer by phase change (liquid to vapour), where energy is absorbed as latent heat, cooling the remaining liquid.
What is Fourier's law?
Fourier's law states that the heat flux due to conduction is proportional to the negative temperature gradient (q = -k ∇T).
What is the difference between conduction and convection?
Conduction occurs through direct contact without bulk motion; convection involves bulk fluid motion carrying heat.
Can heat transfer occur in a vacuum?
Yes, by thermal radiation, which does not require a medium.
What is the role of density in advection?
In advection, heat flux depends on density (ρ), velocity (v), heat capacity (cp), and temperature difference (ΔT).
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