Tag: temperature and heat

Questions Related to temperature and heat

Metal floors cool more than a wood floor in winters because:
physics temperature and heat applications of heat conduction applications of insulation clothes - our necessity

  1. Metal conducts heat more readily than wood

  2. Wood conducts heat more readily than metal

  3. Metal has a higher specific heat than wood

  4. The temperature of the wood is higher than the temperature of the metal

  5. The temperature of the metal is higher than the temperature of the wood

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Correct Option: A
Explanation:

Metals are good conductor of heat whereas wood does not conduct heat at all.

Thus in winters, metal floors cool more than a wood floor.

Which of the following is a good conductor of heat?

physics temperature and heat applications of heat conduction applications of insulation clothes - our necessity

  1. Water and glass

  2. Plastic and copper

  3. Copper and glass

  4. Copper

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Correct Option: D

Ebonite handles are used to handle hot utensil because they are bad conductors of heat.

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

  1. True

  2. False

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Correct Option: A
Explanation:

Yes, it's true that ebonite are bad conductors of heat so they are used to handle hot utensis.

Three rods of identical cross-sectional area and made from the same metal from the sides of an isosceles triangles ABC, right-angled at B. The point A and B are maintained at temperatures T and $(\sqrt{2})$T respectively. In the steady state, the temperature of the point C is $T _C$. Assuming that only heat conduction takes place, $T _C/T$ is?

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

  1. $\dfrac{1}{2\left(\sqrt{2}-1\right)}$

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

  3. $\dfrac{1}{\sqrt{3}\left(\sqrt{2}-1\right)}$

  4. $\dfrac{1}{\sqrt{2}+1}$

Show answer
Correct Option: B

If two bodies A and B of $50^{0} C$ comes in contact with each other. The heat will flow 

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

  1. Body A $\rightarrow$ Body B

  2. Body B $\rightarrow$ Body A

  3. nowhere

  4. from both the bodies

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Correct Option: C
Explanation:

Both the bodies are at same temperature, so there will be no transfer of heat from one body to other body.

If the pressure of a gas is doubled then its thermal conductivity will :

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

  1. remain constant

  2. decrease

  3. decrease exponentially

  4. increase

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Correct Option: A
Explanation:

Thermal conductivity of a gas is independent of the pressure as compared to solid and liquid. So the thermal conductivity of gas will remain constant.

If $K$ denotes coefficient of thermal conductivity, $d$ the density and $C$ the specific heat, the unit of $X$, where $X = K/dc$, will be

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

  1. $cm\space sec$

  2. $cm^2\space sec^{-2}$

  3. $cm \space sec^{2}$

  4. $cm^2 \space sec^{-1}$

Show answer
Correct Option: D
Explanation:

The Units of the respective quantities in SI are:

  • $[K] = J(mKs)^{-1}$
  • $[\rho] = kg(m)^{-3}$
  • $[c] = J(kgK)^{-1}$
$[X] = \dfrac{[K]}{[\rho] [c]} = \dfrac{J(mKs)^{-1}}{(kg(m)^{-3})(J(kgK)^{-1})}$
$[X] = m^{2}s^{-1}$ or in CGS $cm^{2}s^{-1}$

A body of length 1 m have an area of cross-section as 0.75 $m^{2}$. If rate of heat conduction of the body is 6000 J/s and coefficient of thermal conductivity is 200 $Jm^{-1}$ $K^{-1}$, then the temperature difference between the two ends of the body is

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

  1. $30^{\circ}C$

  2. $20^{\circ}C$

  3. $40^{\circ}C$

  4. $80^{\circ}C$

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Correct Option: C

Two rods one hallow and the other solid made of the same material have the same length of $20 cm $ and radius of $2 cm$. When their temperature is increased through the same amount of $50^oC$, their expansion ratio $E _h:E _s$ will be:

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

  1. $1:8$

  2. $1:4$

  3. $1:1$

  4. $1:2$

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Correct Option: A

Equal temperature difference exists between the ends of two metallic rods $1 $ and $2$ of length. Their thermal conductivities are $K _1$ and $K _2$ and cross sectional areas represents $A _1$ and $A _2$. The condition for equal rate of heat transfer is:

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

  1. $K _1A _2=K _2A _1$

  2. $K _1A _1=K _2A _2$

  3. $K _1A _1^2=K _2A _2^2$

  4. $K _1^2A _2=K _2^2A _1$

Show answer
Correct Option: B
Explanation:
Equal temperature difference exists between the two metallic rods 1 and 2.
The heat transfer$=\dfrac{KA \Delta T}{l}$
For equal rate of heat transfer,
$\dfrac{K _1 A _1 \Delta T}{l}=\dfrac{K _2A _2 \Delta T}{l}$
$K _1A _1=K _2A _2$
The correct option is B.