Tag: heat and heat transfer

Questions Related to heat and heat transfer

State whether given statement is True or False
To prevent heat conduction to our hands, handle of cooking vessels are made of bad conductors.

physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Good conductor will transfer the heat from vessel's handle to our hands and let our hands burn. So, bad conductor of heat, materials is used for manufacturing of vessel's handle.

What type of conductor should we used to make water pipes in cold countries?

physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

  1. Good conductor

  2. Poor conductor or bad conductor

  3. Material does not help in such cases

  4. None of the above

Show answer
Correct Option: B
Explanation:

Poor conductor should be used, so that they will not allow heat to pass from water inside the pipe to outside atmosphere to prevent water from freezing. It will help pipes from busting.

State whether given statement is True or False
Woollen yard is a bad conductor of heat. 

physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Woollen sweaters keeps us warm in winter as the air gets trapped in woollen yard.

On a cold day when a room temperature is $15^oC$, the metallic cap of a pen becomes much colder than its plastic body, though both are at the same temperature of $15^oC$, because

physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

  1. metals have higher thermal capacity than plastics

  2. plastics have a lower density than metals

  3. metals are good conductor of heat

  4. plastics have a higher thermal conductivity than metals

Show answer
Correct Option: C
Explanation:

On a cold day when a room temperature is $15^oC$, the metallic cap of a pen becomes much colder than its plastic body, though both are at the same temperature of $15^oC$ because metals are good conductor of heat, so they could absorb and release heat in a better way than insulators.

Two thin walled sphere of different materials ,one with double the radius and one fourth wall thickness of the other are filled with ice If the time taken for complete melting of ice in the sphere of larger radius is $25$ minutes and that for smaller one is $16$ minutes,the ratio of thermal conductivities of the materials of larger sphere to the smaller sphere is  

physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

  1. $4:5$

  2. $25:1$

  3. $1:25$

  4. $8:25$

Show answer
Correct Option: D

Iron, lead and brass spheres of equal masses are heated to a common temperature and are kept on a sheet of wax. The sphere that passes through the plate first is (lead 0.03 $\operatorname { cal } / \mathrm { g } / ^ { \circ } \mathrm { C }$, iron 0.11 $\operatorname { cal } / \mathrm { g } / ^ { \circ } \mathrm { C }$, brass 0.08 $\operatorname { cal } / \mathrm { g } / ^ { \circ } \mathrm { C }$) 

physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

  1. lead

  2. brass

  3. iron

  4. all at the same time

Show answer
Correct Option: D

Glaciers melt:

physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

  1. first at the bootom due to decress in pressure

  2. first at the top due to iuncrease in pressure

  3. first at the bottom due to increase in pressure

  4. first at the top due to increase in pressure

Show answer
Correct Option: C

Two rods having thermal conductivities in the ratio of 5:3 and having equal length length and equal cross-section are joined by face to face. If the temperature of free end of first rod is $100^oC$ and temperature of  free end of second rod is $20^oc$, then temperature of the junction, is-

physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

  1. $90^oC$

  2. $85^oC$

  3. $70^oC$

  4. $50^oC$

Show answer
Correct Option: C
Explanation:

Let the thermal conductivity of first rod be $5 K$

Let the thermal conductivity of second rod be $3 k$
now, sum of heat current flowing through the junction =0
$\begin{array}{l} \frac { { 5KA\left( { 100-T } \right)  } }{ x } +\frac { { 3KA\left( { 20-T } \right)  } }{ x } =0 \ 500-5T+60-3T=0 \ 8T=560 \ \therefore T={ 70^{ 0 } }C \end{array}$

Select and write the most appropriate answer from the given aternative in question:
Which of the following substances is ductile?

physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

  1. Glass

  2. High carbon steel

  3. Steel

  4. Copper

Show answer
Correct Option: C

Two walls of thickness $d _1$ and $d _2$, thermal conductivities $K _1$ and $K _2$ are in contact. In the steady state if the temperatures at the outer surfaces are $T _1$ and $T _2$, the temperature at the common wall will be

physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

  1. $\dfrac{K _1T _1+K _2T _2}{d _1+d _2}$

  2. $\dfrac{K _1T _1d _2+K _2T _2d _1}{K _1d _2+K _2d _1}$

  3. $\dfrac{(K _1d _1+K _2d _2)T _1T _2}{T _1+T _2}$

  4. $\dfrac{K _1d _1T _1+K _2d _2T _2}{K _1d _1+K _2d _2}$

Show answer
Correct Option: B