Tag: conduction

Questions Related to conduction

A spherical black body of radius $(R)$ when heated to certain temperature and left in vaccum. cools at a rate $'x' $ Now a caity of radius $(R/2)$ is made concentrically from this sphere. The rate of cooling of the remaining sphere will be.....................

physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

  1. $\cfrac { x }{ 8 } $

  2. $\cfrac { 7x }{ 8 } $

  3. $\cfrac { 8x }{ 8 } $

  4. $\cfrac { x }{ 7 } $

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Correct Option: A

A hollow copper sphere and a hollow copper cube, of same surface area and negligible thickness, are filled with warm water of same temperature and placed in an enclosure of constant temperature, a few degrees below that of the bodies. Then in the beginning:

physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

  1. the rate of energy lost by the sphere is greater than that by the cube

  2. the rate of fall of temperature for sphere is greater than that for the cube.

  3. the rate of energy lost by the sphere is less than that by the cube

  4. the rate of fall of temperature for sphere is less than that for the cube.

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Correct Option: B

A spherical body of radius n. If its rate of cooling is R, then

physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

  1. $R \propto \frac{1}{n}$

  2. $R \propto \frac{1}{n^2}$

  3. $R \propto n$

  4. $R \propto n^2$

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Correct Option: C

A copper block of mass $500gm$ and $Sp.$ Heat $0.1 cal/gm/^{o}{C}$ is heated from ${30}^{o}C$ to ${40}^{o}C$. Another identical copper block $B$ of same mass is heated from ${35}^{o}C$ to ${40}^{o}C$. The ratio of their thermal capacities is 

physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

  1. $1:2$

  2. $2:1$

  3. $1:1$

  4. $1:4$

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Correct Option: C

Heat required to convert one gram of ice at $0^{ _-^0}C$ into steam at $100^{ _-^0}C$ is (given $L _{steam}$ = 536 cal/gm)-

physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

  1. 100 calorie

  2. 0.01 kilocalorie

  3. 716 calorie

  4. 1 kilocaorie

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Correct Option: C

Air is filled at $60^o$C in a vessel of open mouth. The vessel is heated at temperature T so that $\dfrac{1}{4}$ th part of air escapes. Assuming volume of container remaining constant, find value of T. 

physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

  1. $80^oC$

  2. $444^oC$

  3. $333^oC$

  4. $171^oC$

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Correct Option: D

Cooking utensils are made up of 

physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

  1. Good conductors of heat

  2. bad conductors of heat

  3. neither good conduction not bad conductors of heat

  4. None of these

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Correct Option: A

$1\ kcal $ per hour of heat flowing through a rod of iron. When the rod is cut down to $4$ pieces then what will be the heat flowing through each piece having same differential temperature?

physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

  1. $1 / 2\ \mathrm { kcal }$

  2. $1 / 4\ \mathrm { kcal }$

  3. $1\ \mathrm { kcal }$

  4. $1 / 15\ \mathrm { kcal }$.

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Correct Option: A

A metal rod of length $2m$ has cross sectional area $2A$ and as shown in figure$.$ The ends are maintained at temperature $100^0C$ and $70^0C$.$ The tem[temperature at middle point C is

physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

  1. $90^0C$

  2. $30^0C$

  3. $45^0C$

  4. $60^0C$

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Correct Option: A
Explanation:

$\begin{array}{l} Let\, \, q\, \, be\, \, temperatrure\, \, middle\, \, po{ { int } }\, \, C\, and\, \, in\, \, series\, \, rate\, \, of\, \, heat\, \, flow\, \, is\, \, same \ K\left( { 2A } \right) \left( { 100-\theta  } \right) =KA\left( { \theta -70 } \right)  \ 200-2\theta =\theta -70 \ 3\theta =270 \ \theta ={ 90^{ 0 } }C \end{array}$

Hence,
option $(A)$ is correct answer.

The thermal conductivity of a rod depends on :

physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

  1. length

  2. mass

  3. area of cross-section

  4. material of rod

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Correct Option: D
Explanation:

Thermal conductivity is a material property.
It does not depend on area of cross section, length and mass of the rod.
option (D) is the correct answer.