Tag: temperature and heat

Questions Related to temperature and heat

Two thermometers are used to record the temperature of a room. If the bulb of one is wrapped in wet hanky:

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

  1. The temperature recorded by both will be same.

  2. The temperature recorded by the wet-bulb thermometer will be greater than that recorded by the other.

  3. The temperature recorded by dry-bulb thermometer will be greater than that recorded by the other

  4. None of the above

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Correct Option: C
Explanation:

The thermometer whose bulb is wrapped by wet hanky; undergoes evaporation process; and we know that evaporation results in cooling, so the wet bulb, thermometer will record less temperature than that of dry bulb thermometer.

Two plates of same thickness form a composite plate. The temperature on one side of the plate is $0^0 C$. If the ratio of thermal conductivities is 3 : 1 and the plate with higher thermal conductivity has one of its faces at $0^0 C$, then the temperature of the interface is 

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

  1. $45^0 C$

  2. $40^0 C$

  3. $20^0 C$

  4. $15^0 C$

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Correct Option: D

A body P is connected to a large body Q through a conducting rod of length. I crossectional  area. A and thermal conductivity K. This assembly is placed in an an atmosplere of temperature ${ T } _{ A }$ and body Q is also maintained at temperature ${ T } _{ A }$. Let beat capacity of body P is C and it is unitally at temperature ${ T } _{ 1 }$. If in time t second temperature of body P falls to ${ T } _{ 2 }$. Then chose the correct option .

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

  1. $log\left[ \dfrac { { T } _{ 2 }-{ T } _{ A } }{ { T } _{ 1 }-{ T } _{ A } } \right] =\left[ { K } _{ 1 }\dfrac { KA }{ LC } \right] t$

  2. $log\left[ \dfrac { { T } _{ 2 }-{ T } _{ A } }{ { T } _{ 12 }-{ T } _{ A } } \right] =\left[ { K } _{ 1 }\dfrac { KA }{ LC } \right] t$

  3. $log\left[ \dfrac { { T } _{ 1 }-{ T } _{ A } }{ { T } _{ 2 }-{ T } _{ A } } \right] =\left[ { K } _{ 1 }\dfrac { KA }{ LC } .t \right]$

  4. $log\left[ \dfrac { { T } _{ 1 }-{ T } _{ A } }{ { T } _{ 2 }-{ T } _{ A } } \right] =\left[ { K } _{ 1 }\dfrac { KA }{ LC } \right] t$

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Correct Option: C

The dimensions of coefficient of thermal conductivity is:

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

  1. $M \ L^{.2} T^{.2} K^{.1}$

  2. $M \ L \ T^{.-3} K^{.-1}$

  3. $M \ L \ T^{.2} K^{.1}$

  4. $M \ L \ T^{.3} K$

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Correct Option: B
Explanation:

The dimension of coefficient of thermal conductivity is ${M^1}{L^1}{T^{ - 3}}{K^{ - 1}}$ 

Hence,
option $B$ is correct answer.

A wall has two layers A and B, each made of different material. Both the layers have the same thickness. The thermal conductivity of the material of A is twice that of B. Under thermal equilibrium, the temperature difference across the wall is $36^o$C. The temperature difference across the layer A is?

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

  1. $6^o$C

  2. $12^o$C

  3. $18^o$C

  4. $24^o$C

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Correct Option: B

a wall has two layers $A$ and $B,$ each made of  a different material.Both the layers have the same thickness.The thermal conductivity of the material of $A$ is twice that of $B.$ Under thermal equilibrium, the temperature difference across the wall is ${36^ \circ }C$ The temperature difference across the layer $A$ is  

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

  1. ${6^ \circ }C$

  2. ${12^ \circ }C$

  3. ${18^ \circ }C$

  4. ${24^ \circ }C$

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Correct Option: C

An aluminium meter rod of area of cross section $4cm^2$ with K=0.5 cal $g^{-1}$ $^oC^{-1}$ is observed that at steady state 360 cal of heat flows per minute.
The temperature gradient along the rod is

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

  1. $3^oC/cm$

  2. $6^oC/cm$

  3. $12^oC/cm$

  4. $20^oC/cm$

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Correct Option: A

A conducting ring lies fixed on a horizontal plane. If a charged nonmagnetic particle is released from a point (on the axis) at some height from the plane, then :

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

  1. an induced current will flow in clockwise or anticlockwise direction in the loop depending upon the nature of the charge

  2. the acceleration of the particle will decrease as it comes down

  3. the rate of production of heat in the ring will increase as the particle comes down

  4. no heat will be produced in the ring

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Correct Option: D

Ratio of radius of curvature of cylindrical emitters of same type is $1:4$ and their temp. are in ration $2:1$. Then ration of amount of heat emitted by them is-(For Cylinder length = radius);-

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

  1. 2:1

  2. 1:1

  3. 4:1

  4. 1:4

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Correct Option: B

If the coefficient of conductivity of aluminium is $0.5cal/cm-sec-^oC,$ then in order to conduct $10cal/sec-cm^2$ in the steady state, the temperature gradient in aluminium must be

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

  1. $5^oC/cm$

  2. $10^oC/cm$

  3. $20^oC/cm$

  4. $10.5^oC/cm$

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Correct Option: C