Tag: thermal energy transfers

Questions Related to thermal energy transfers

A solid sphere and a hollow sphere of same material and size are heated to some temperature and allowed to cool in the same surroundings.If the temperature difference between each sphere and its surrounding is T, then:-

conduction in metals and non-metals thermal energy transfers physics

  1. The hollow sphere will cool at a faster rate for all values of T

  2. The solid sphere will cool at a faster rate for all values of T

  3. Both spheres will coll at the same rate for all values of T

  4. Both spheres will coll at the same rate only for small values of T

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Correct Option: C

Two identical bodies are made of a material for which the heat capacity increases with temperature. One of these is at ${ 100 }^{ 0 }$, while the other one is at ${ 0 }^{ 0 }C$. If the two bodies are brought into contact, then assuming no heat loss, the final common temperature is

conduction in metals and non-metals thermal energy transfers physics

  1. ${ 50 }^{ 0 }C$

  2. more than ${ 50 }^{ 0 }C$

  3. less than ${ 50 }^{ 0 }C$ but greater than ${ 0 }^{ 0 }C$

  4. ${ 0 }^{ 0 }C$

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Correct Option: A

When a thermometer is taken from the melting ice to a warm liquid, the mercury level rises to two-fifths of the distance between the lower and the upper fixed points. Find the temperature of the liquid $(i)i{n^o}C,and(ii)\;in\;K.$ 

conduction in metals and non-metals thermal energy transfers physics

  1. ${40^0}C.313K$

  2. ${30^0}C.227K$

  3. ${20^0}C.273K$

  4. ${0^0}C.0K$

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Correct Option: A

In winter , temprature of bottom of take is 4$$C . Ratio of thermal conductance of ice and water is 2:3 and depth of the take 20 m. Find the maximum thickness os ice formed .  

conduction in metals and non-metals thermal energy transfers physics

  1. $\frac { 200 }{ 11 } M$

  2. $\frac { 100 }{ 8 } M$

  3. $\frac { 220 }{ 12 } M$

  4. 10 M

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Correct Option: C

A semicircular rod is joined at its end to a straight rod of the same material and the same cross-sectional area. The straight rod forms a diameter of the other rod. The junctions are maintained at different temperatures. Find the ratio of the heat transferred through a cross-section of the semicircular rod of the heat transferred through a cross-section the straight rod in the given time.

conduction in metals and non-metals thermal energy transfers physics

  1. $\dfrac 2\pi$

  2. $\dfrac 1\pi$

  3. $\dfrac 1{2\pi}$

  4. $\dfrac \pi2$

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Correct Option: A

Bimetallic thermostat consists two metals of different thermal co-efficient thermostat always bends towards material having
(i)large thermal expansion on heating 
(ii)large thermal expansion on cooling
(iii)small thermal expansion on heating
(iv)small thermal expansion on cooling

conduction in metals and non-metals thermal energy transfers physics

  1. I only

  2. II only

  3. III and II only

  4. I and IV only

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Correct Option: C

The ratio of radii of two spheres of same material is  $1:4 .$  Then the ratio of their heat  capacity will be

conduction in metals and non-metals thermal energy transfers physics

  1. $\dfrac { 1 } { 64 }$

  2. $\dfrac { 1 } { 32 }$

  3. $\dfrac { 1 } { 2 }$

  4. $\dfrac { 1 } { 4 }$

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Correct Option: C

A heat engine takes steam at $200^oC$ and after doing work exhausts it directly into air at $100^oC$. Calculate the percentage of heat which is wasted.

conduction in metals and non-metals thermal energy transfers physics

  1. $58.86$

  2. $68.86$

  3. $48.86$

  4. $78.86$

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Correct Option: B

Which of the following material is most suitable for cooking utensil ?

conduction in metals and non-metals thermal energy transfers physics

  1. Low conductivity and low specific heat

  2. High conductivity and low specific heat

  3. Low conductivity and High specific heat

  4. High conductivity and High specific heat

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Correct Option: A

Two angular blocks A and B different metal have same length and same area of cross-section . they are kept in such a way that their cross-sectional area touch each other. the temperature at one end of A is $ 100^0 $ C and that of B at the other end is $0^0 C $ C . if the ratio of their conductivity is 1:3 then under steady state, the temperature of the junction in contact will be:-

conduction in metals and non-metals thermal energy transfers physics

  1. $ 25^0 C $

  2. $ 50^0 C $

  3. $ 75^0 C $

  4. $ 100^0 C $

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Correct Option: C