Tag: transfer of heat

Quizzes (8) Questions (172)

Questions Related to transfer of heat

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.

Multiple choice physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

A geyser heats water flowing at the rate of 4 litre per minutes from 30 C to 85 C. If the geyser operates on gas burner then the amount of heat used per minute is :

  1. $9.24\times { 10 }^{ 5 }$J

  2. $6.24\times { 10 }^{ 7 }$J

  3. $9.24\times { 10 }^{ 7 }$J

  4. $6.24\times { 10 }^{ 5 }$J
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

For one minute

$H=mC\theta$
$=4kg\times 4200\times55\=924000J\=9.24\times 10^5j$

Multiple choice physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

A 2 m long wire of resistance 4 ohm and diameter 0.64 mm is coated with plastic insulation of thickness 0.06 mm, when a current of 5 ampere flows through the wire, find the temperature difference across the insulation in steady state if $k=0.16\times { 10 }^{ -2 }cal/\left( cm{ C }^{ 0 }sec \right) $ 

  1. ${ 3 }^{ \circ }C$

  2. ${ 2 }^{ \circ }C$

  3. ${ 4 }^{ \circ }C$

  4. ${ 1 }^{ \circ }C$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The temperature difference across cylindrical insulation is given by ΔT = Q × ln(r2/r1) / (2πkL), where Q = I²R. For the given values (wire radius 0.32mm, insulation thickness 0.06mm, k=0.16×10⁻², L=200cm, Q=5²×4=100W), the temperature difference works out to approximately 3°C. The insulation thickness is small compared to wire radius, which affects the logarithmic term in the heat transfer equation.

Multiple choice physics heat energy transfers heat and heat transfer heat energy transfer transfer of heat

Name a medium which is a good insulator of heat.

  1. Still (or trapped) air

  2. Oil

  3. Steam

  4. solid copper
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Trapped(still) air is good insulator.
Thermal conductivity of air is small as compared to solid and liquid. Eg- glass conducts 30 times more power per unit distance per unit temperature than air.
The less dense the material, the less thermal conductivity. And gas(air) is least dense than solid and liquid.