Tag: applications of heat conduction

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Questions Related to applications of heat conduction

Multiple choice physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

State the correct statement

  1. When we heat an object, it becomes hot

  2. When we heat an object, it expands in size

  3. When we heat an object, it changes its such such as water boils to form water vapour

  4. All of them are true
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

When we heat an object, it changes its shape, nature and it becomes hot, the temperature increases due to movement of atoms.

Multiple choice physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

The ............ the conductor, the more rapidly does heat transfer takes place.

  1. better

  2. worse

  3. thinner

  4. thicker
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The better the conductor, the more rapidly does heat transfer takes place .


Better conductor means more thermal conductivity; more the thermal conductivity; more rapidly the heat transfer takes place.

Multiple choice physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

The reason for providing copper bottoms in steel pans is :

  1. aesthet, carly looks good

  2. that copper is better conductor than steel

  3. that copper is not a good conductor than steel

  4. None of the above 
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Copper bottoms are provided in steel pans because copper is better conductor of heat than steel.

Thermal conductivity of copper is highest ($38600w/mK$) while that of steel is lowest ($1245w/mK$).

Multiple choice physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

Four rods of same material but with different radii and lengths are used to connect two reservoirs of heat with the same temperature difference. Which one will conduct more heat

  1. r=1 cm, 1=1 cm

  2. r=1 cm, 1= 2 cm

  3. r= 1 cm, $1=\frac{1}{2}m$

  4. $r=\frac{1}{2}cm$, $1=\frac{1}{2}m$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Heat conduction rate H = k*A*(delta T)/L. Since material and delta T are constant, H is proportional to A/L, or (r^2)/L. Calculating r^2/L for each: A) 1/1=1, B) 1/2=0.5, C) 1/0.5=2, D) 0.25/0.5=0.5. Option C gives the highest value.

Multiple choice physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

What will be the conductivity of pure silicon crystal at 300 K temperature if  electron cottoer pair at this temperature is $ 1.072 \times 10^{10} /cm^3 $ and $ \mu _n = 1350 cn^2 /V-s and \mu _p = 480 cm^2/ V-s $ ?

  1. $ 3.14 \times 10^{-4} mho /cm $

  2. $ 3.14 \times 10^{-5} mho /cm $

  3. $ 3.14 \times 10^{-6} mho /cm $

  4. $ 3.14 \times 10^{3} mho /cm $
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

The heat capacity of a body depends on 

  1. the heat given

  2. the temperature rasied

  3. the mass of the body

  4. the material of he body.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Heat capacity (C) is defined as the amount of heat required to raise the temperature of a body by one degree. It is given by C = m * c, where m is the mass and c is the specific heat capacity of the material.

Multiple choice physics transfer of heat applications of heat conduction applications of insulation clothes - our necessity

In a steady state of thermal conduction, temperature of the ends $A$ and $B$ of a $20cm$ long rod are $100^oC$ and $0^oC$, respectively. What will be the temperature of the rod at a distance of $6cm$ from the end $A$ of the rod?

  1. $-30^oC$

  2. $70^oC$

  3. $5^oC$

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In steady state, the temperature gradient is linear. Temperature T(x) = T_A - (T_A - T_B) * (x / L). T(6) = 100 - (100 - 0) * (6 / 20) = 100 - 100 * 0.3 = 100 - 30 = 70 degrees Celsius.