Tag: transfer of heat

Questions Related to transfer of heat

If we keep pop corn in a pressure cooker on a flame, heat is transferred from flame to corn by :

physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

  1. Conduction

  2. Radiation

  3. Convection

  4. None

Show answer
Correct Option: A
Explanation:

The direct contact of cooker and corn is an example of conduction.

The molecules of medium vibrate about their mean positions during heat transfer in the process of

physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

  1. Conduction

  2. Radiation

  3. Convection

  4. None

Show answer
Correct Option: A
Explanation:

The molecules of medium transfer heat as they vibrate about mean position in conduction.
The molecules of medium absorb heat, they rise and other molecules of medium come to take their place convection
In radiation, medium does not play role.

Air is a bad conductor of heat because:

physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

  1. it's molecules are in continuous contact with each other.

  2. it's molecules are not in continuous contact with each other

  3. it's molecules absorb all the heat

  4. it's molecules are moving randomly due to Brownian motion

Show answer
Correct Option: B
Explanation:
Air is a bad conductor of heat because it's molecules are not in continuous contact with each other.
Air molecules are too far to disperse heat energy to one another efficiently. Heat is conducted by molecules and atoms that are very closely bonded together and vibrating at high frequency.

.................. surface absorbs more heat than any other surface under identical conditions.

physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

  1. White & Shiny

  2. White & Rough 

  3. Black & Rough

  4. Yellow & Shiny

Show answer
Correct Option: C
Explanation:
Black & rough surface absorbs more heat than any other surface under identical conditions.
Black surface absorbs all the radiations more easily than any surface as its absorptivity is $1$.

The heat transfer in air is poor because

physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

  1. it take place mainly due to convection

  2. it take place mainly due to conduction

  3. it take place mainly due to radiation

  4. all of the above

Show answer
Correct Option: A
Explanation:

Air is a gas and its molecules are far apart from each other. So, this is not a good condition for conduction. Also, air being a non-metal doesn't have free electrons for conduction. Hence option B is not applicable.

C is also not applicable because radiation doesn't need any medium. Air being a fluid, convection can take place through it. But convection is not a very fast mode of transfer of heat.

Seema is planning a trip to Kashmir this summer. Which of the following clothes should she definitely pack?

physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

  1. Denim Jacket

  2. Leather pants

  3. Woolen sweater

  4. Cotton shirt

Show answer
Correct Option: C
Explanation:

She must pack the woolen sweater, because even in summer; Kashmir's climate will definitely too much cool. As wool is good insulator of heat; it insulates body from the surrounding. And the air which is trapped between woolen fabrics. It prevents the flow of heat from the body; as air is also bad conductor of heat. So as a result the heat present in the body remains trapped in the body; it can't escape to atmosphere.

Which of the following is not a valid reason for using cotton clothes in Summer ?

physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

  1. Cotton clothes attract cool air.

  2. Cotton clothes absorb sweat from the body.

  3. Cotton exposes the sweat to atmosphere for evaporation

  4. Cotton is light in weight.

Show answer
Correct Option: A
Explanation:

We wear cotton clothes during summer as cotton absorbs sweat from the body exposing to the atmosphere for easy evaporation. As we tend to sweat more during summer and cotton fabric absorb sweat and help body to cool down. Cotton allows better air circulation which helps to absorb and removing body moisture caused by sweat via evaporation cotton fabric is very light in weight.

Why do we wear cotton clothes in Summer ?

physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

  1. Cotton is a bad conductor of heat and doesn't allow passage of warmer air near body.

  2. Cotton is a good conductor of heat and allows body heat to escape in the atmosphere.

  3. Cotton absorbs sweat from the body, exposing it to atmosphere for easy evaporation

  4. None of the above

Show answer
Correct Option: C
Explanation:

We wear cotton clothes during summer as cotton absorbs sweat from the body, exposing to the atmosphere for easy evaporation. As we tend to sweat more during summer and cotton fabric absorbs sweat and help body to cool down. Cotton allows better air circulation which helps to absorb and removing body moisture caused by sweat via evaporation.

Which of the following is a wrong pair of clothes worn during a particular season ?

physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

  1. Cotton clothes during summer

  2. Woolen clothes during winter

  3. Dark colored clothes during summer

  4. Polyester raincoats during Rainy season

Show answer
Correct Option: C
Explanation:

Dark coloured clothes during summer is a wrong pair of clothes. As during summer, heat present in the atmosphere and surrounding is too much. And when dark colored clothes are the worm, as we know dark color absorbs more heat than any other color. So it will increase the heat felt by our body during summer.

Wool is used in making garments used in winter because

physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

  1. Wool is a good conductor of heat

  2. Wool is a bad conductor of heat

  3. Air, trapped in between the wool fibres, prevents the flow of heat from our body to the cold surroundings.

  4. Both B and C

Show answer
Correct Option: D
Explanation:

Wool is used in making garments used in winter because wool is bad conductor of heat; it insulates the body from the surrounding. And the air which is trapped in between the wool fibers; prevents the flow of heat from our body to the cool surrounding. As air is the bad conductor of heat too it also insulates the body with wool.