Physics · Science General

Heat Transfer Mechanisms

828 Questions

Heat Transfer Mechanisms deal with the movement of thermal energy through conduction, convection, and radiation. It involves practical applications like ocean heat storage and atmospheric heating. These fundamental physics concepts are frequently asked in general science sections.

Thermal conductionHeat convectionThermal radiationSpecific heatStates of matter

Heat Transfer Mechanisms Questions

Multiple choice thermo flask thermos flask heat energy transfers transfer of heat physics

A thermos flask is designed to prevent the contents of the flask from losing heat. Which of the following statements concerning the design of thermos flasks is incorrect?

  1. The stopper helps reduce heat loss by convection

  2. The glass walls are silver coated to reduce emitted radiation

  3. The flask is designed to prevent heat loss by conduction, convection and radiation

  4. The vacuum between the glass walls prevents heat loss by preventing radiation
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Yes, thermoflask is designed to prevent  the contents of the flask from losing heat.
The stopper, i.e. vacuum between double walls of thermoflask prevents heat transfer through convection.
The glass walls are silver coated because it reduces emitted radiation when they are silver coated i.e. made shiny. And we know that shiny surfaces reflects all the heat so all the heat is being reflected inside the walls and heat remains unaffected. And the thinesss of glass walls will stop heat entering or leaving the flask by conduction.
So, the flask is designed to prevent heat loss by conduction, convection and radiation.
Multiple choice thermo flask thermos flask heat energy transfers transfer of heat physics

Vacuum in a vacuum flask prevents heat transfer through process of-

  1. Conduction only

  2. Conduction and Convection

  3. Convection only

  4. Radiation only
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Vacuum in a vacuum flask prevents heat transfer through process of conduction and convection.
It is so because, in conduction there needs a direct contact for transfer of heat and there is vaccum between two layers, so conduction can't  transfer heat in this case. And in convection, heat is transferred by molecular motion in fluid (liquid or gas). But due to vaccum's presence between two layers, molecular motion is not possible So convection is also impossible for this case.
Multiple choice thermo flask thermos flask heat energy transfers transfer of heat physics

The silver coating on the inner bottle of a thermos flask

  1. prevents heat transfer by conduction

  2. prevents heat transfer by convection

  3. prevents heat transfer by radiation

  4. prevents heat transfer by absorption
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Due to the silver coating on the inner bottle, a shiny surface is formed. And these shiny surface act as a good reflector of heat 
As a result, they prevent the transfer of heat by radiation.
Multiple choice thermo flask thermos flask heat energy transfers transfer of heat physics

The walls of thermo-flask are polished because

  1. shining bodies are good absorber of heat

  2. shining bodies are good radiator of heat

  3. shining bodies have emisivity as one

  4. none of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The wall of thermoflask are polished because shiny surface are good radiators of heat. Since we intend to keep in the vacuum flask and not have it radiated, Outside the shiny surface is best option. A black wall is bad option as they are good emitter and absorber of heat radiation.

Multiple choice thermo flask thermos flask heat energy transfers transfer of heat physics

The vacuum between the walls of the flask prevents the transfer of heat by

  1. Conduction

  2. Convection

  3. Radiation

  4. All
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Thermos flask is a special kind of bottle used for keeping the hot liquid hot and the cold liquid cool for a sufficiently long time. It was deviced by sir James Dewar and do it is also known as Dewar Flask. The vacuum between the walls of the flask prevents the transfer of  heat by conduction.

Multiple choice thermo flask thermos flask heat energy transfers transfer of heat physics

A polished silver surface is

  1. good absorber of heat

  2. good reflector of heat

  3. poor reflector of heat

  4. none of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Heat rays are electromagnetic rays. Light rays are also electromagnetic rays. We know that a polished silver surface is a good reflector of light. this means that it is a good reflector of electromagnetic rays. Hence it is a good reflector of heat

Multiple choice thermo flask thermos flask heat energy transfers transfer of heat physics

A thermos flask maintains temperature of objects. It

  1. containing some kind of heating element to keep hot things hot.

  2. containing some kind of heating element to keep cold things cold.

  3. keeps hot things hot by not allowing heat to escape.

  4. All of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
A thermos flask maintains temperature of objects. It keeps hot things hot by not allowing heat to escape.
Thermos flask doesn't allow heat to escape from it via any mode of heat transfer i.e. conduction, convection, radiation. It does so by silver coating or polishing inner surface thin walls and vacuum between two walls.
Multiple choice thermo flask thermos flask heat energy transfers transfer of heat physics

A themoflask prevent heat loss from-

  1. Conduction

  2. Convection

  3. radiation

  4. all of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
A thermoflask prevent heat loss from conduction, convection and radiation.
As it has insulator between two layers, it prevents the direct contact with surrounding and also stops the molecular motion for heat transfer. As it is a closed system surrounded by the layer of insulator, radiation can't even take place.
Multiple choice temperature control homeostasis coordination and response biology

Mechanism for cooling of human body is

  1. Sweating

  2. Crying

  3. Laughing

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
  • Sweating from sweat glands, often in response to heat, exercise or stress.
  • Sweating is also called as Perspiration. is the production of fluids secreted by the sweat glands in the skin of mammals. 
  • In humans, sweating is primarily a means of thermoregulation, which is achieved by the water-rich secretion of the eccrine glands. 
  •  Evaporation of sweat from the skin surface has a cooling effect due to evaporative cooling. Hence, Mechanism for cooling of the human body is Sweating. 
 So, the correct answer is 'Sweating'.
Multiple choice temperature control homeostasis coordination and response biology

Temperature of human body is maintained by

  1. Perspiration

  2. Conduction and convection

  3. Radiation

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
  • Core temperature is regulated by the hypothalamus (in the brain), which is often called the body’s thermostat. 
  • The hypothalamus responds to various temperature receptors located throughout the body and makes physiological adjustments to maintain constant core temperature. 
  • The human body regulates temperature by keeping a tight balance between heat gain(conduction) and heat loss(convention). And in humans, perspiration (sweating) is primarily a means of thermoregulation. Hence, Temperature of the human body is maintained by Perspiration, Conduction and convection and Radiation. So, the correct answer is 'All of the above'.
Multiple choice temperature control homeostasis coordination and response biology

What is the effect of shivering in raising the body temperature during cold weather?

  1. Shivering dilates blood vessels

  2. Shivering constricts blood vessels

  3. Shivering increases the heart rate

  4. Shivering stimulates rapid muscle action

  5. Shivering tightens skin to cause goose bumps
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Our body needs to maintain a 37°C to function properly. If it drops it could damage our organs or brain, so to stop this happening, our body strictly regulates temperature. Shivering is an involuntary pattern of repetitive, rhythmic muscle contractions. This twitching exercise produces heat, which helps to raise body temperature. Thus, the correct answer is option D.

Multiple choice temperature control homeostasis coordination and response biology

If the external temperature is low 

  1. Warm receptors are activated.

  2. Warm receptors are inhibited.

  3. Thermostat becomes operational ordering vasoconstriction of peripheral vessels and stimulation of skeletal muscles.

  4. Thermostat becomes operational ordering vasoconstriction of peripheral vessels and activation of sweat glands.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When the external temperature is low, the hypothalamus (the body's thermostat) triggers mechanisms to conserve and generate heat, such as vasoconstriction (to reduce heat loss at the skin) and shivering (to generate heat via muscle activity).

Multiple choice modelling gases - the kinetic model ideal gases kinetic theory of gases physics

Heat is associated with 

  1. kinetic energy of random motion of molecules

  2. kinetic energy of orderly motion of molecules

  3. total kinetic energy of random and orderly motion of molecules

  4. kinetic energy of random motion in some cases and kinetic energy orderly motion in other.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Heating up a substance excites the molecules of that substance making  the molecules moves vigorously thus giving velocity to the molecules and we know kinetic energy of a body is by the virtue of its motion.