Tag: transfer of heat

Quizzes (8) Questions (172)

Questions Related to transfer of heat

Multiple choice physics transfer of heat applications of convection convection thermal energy transfers

A sphere of density d, statisfied heat s and radius r is hung by thermally insulating thread in an enclosure which is kept at a lower temperature than the sphere.The temperature of the sphere to drop at a rate which depends upon the temperature difference between the and the enclosure,If the temperature difference is $ \triangle T $ and surrounding temperature is $ T _o $ then rate of fall in temperature will be-

  1. $ \frac {4 \sigma T _o^2 \triangle T}{rdc} $

  2. $ \frac {12 \sigma T _o^2 \triangle T}{rdc} $

  3. $ \frac {12 \sigma T _o^4 \triangle T}{rdc} $

  4. $ \frac {12\sigma \triangle T}{rdc T _o^3 } $
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice physics transfer of heat applications of convection convection thermal energy transfers

The correct statement of the following:
A) Water can be boiled inside the artificial satellite by convection
B) Heavy liquid can be boiled in artificial satellite by convection
Mark correct option/s

  1. Both statements are correct

  2. Both statements are wrong

  3. A is correct but B is wrong

  4. B is correct but A is wrong
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Conduction and Convection are non-existent in space, so both the statements are wrong. 

Multiple choice physics transfer of heat applications of convection convection thermal energy transfers

It is hotter at some distance over the flames than in front of it because :

  1. air conducts heat upwards only

  2. heat is radiated upwards only

  3. convection of heat occurs upwards only

  4. heat is radiated downwards only
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Near flames, heat transfer occurs by both convection and radiation (and some conduction too).
But convection occurs only in upward direction. So, above the flame, it is hotter rather than in front of the flame.

Multiple choice physics transfer of heat applications of convection convection thermal energy transfers

Which of the following process(es) occur(s) during the convective transfer of heat within a large volume of air? 

  1. A continuous flow of warmer and cooler parts of air is established.

  2. The flow of air molecules results in flow of heat.

  3. The cooler portion of the air surrounding a warmer part exerts a buoyant force on it.

  4. As the warmer part of the air moves, it is replaced by cooler air that is subsequently warmed up.
Reveal answer Fill a bubble to check yourself
A,B,C,D Correct answer
Explanation

A continuous flow of warmer and cooler parts of air is established in which the air molecules are responsible for flow of heat. As the warmer air molecules move up, they are replaced bu cooler air molecules.

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

__and__are good conductors of heat

  1. Silver, Copper

  2. Wood,Plastic

  3. Glass,Paper

  4. Pure water,Iron
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Silver and copper are good conductors of heat.
$\because$ Silver and copper are only metals present there and as we know metals have conductivity of heat and electricity than non-metal and metalloids. So, silver and copper are god conductors of heat.
Multiple choice physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

State the correct statement

  1. When we heat an object, it becomes hot

  2. When we heat an object, it expands in size

  3. When we heat an object, it changes its such such as water boils to form water vapour

  4. All of them are true
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

When we heat an object, it changes its shape, nature and it becomes hot, the temperature increases due to movement of atoms.

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

The ............ the conductor, the more rapidly does heat transfer takes place.

  1. better

  2. worse

  3. thinner

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

The better the conductor, the more rapidly does heat transfer takes place .


Better conductor means more thermal conductivity; more the thermal conductivity; more rapidly the heat transfer takes place.

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

The reason for providing copper bottoms in steel pans is :

  1. aesthet, carly looks good

  2. that copper is better conductor than steel

  3. that copper is not a good conductor than steel

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

Copper bottoms are provided in steel pans because copper is better conductor of heat than steel.

Thermal conductivity of copper is highest ($38600w/mK$) while that of steel is lowest ($1245w/mK$).

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

Four rods of same material but with different radii and lengths are used to connect two reservoirs of heat with the same temperature difference. Which one will conduct more heat

  1. r=1 cm, 1=1 cm

  2. r=1 cm, 1= 2 cm

  3. r= 1 cm, $1=\frac{1}{2}m$

  4. $r=\frac{1}{2}cm$, $1=\frac{1}{2}m$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Heat conduction rate H = k*A*(delta T)/L. Since material and delta T are constant, H is proportional to A/L, or (r^2)/L. Calculating r^2/L for each: A) 1/1=1, B) 1/2=0.5, C) 1/0.5=2, D) 0.25/0.5=0.5. Option C gives the highest value.