Tag: thermal energy transfers

Quizzes (4) Questions (47)

Questions Related to thermal energy transfers

Multiple choice conduction in metals and non-metals thermal energy transfers physics

A solid sphere and a hollow sphere of same material and size are heated to some temperature and allowed to cool in the same surroundings.If the temperature difference between each sphere and its surrounding is T, then:-

  1. The hollow sphere will cool at a faster rate for all values of T

  2. The solid sphere will cool at a faster rate for all values of T

  3. Both spheres will coll at the same rate for all values of T

  4. Both spheres will coll at the same rate only for small values of T
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

According to Newton's law of cooling, the rate of cooling depends on the surface area and emissivity. Since the spheres have the same material, size, and surroundings, they have the same surface area and emissivity, resulting in the same rate of cooling.

Multiple choice conduction in metals and non-metals thermal energy transfers physics

Two identical bodies are made of a material for which the heat capacity increases with temperature. One of these is at ${ 100 }^{ 0 }$, while the other one is at ${ 0 }^{ 0 }C$. If the two bodies are brought into contact, then assuming no heat loss, the final common temperature is

  1. ${ 50 }^{ 0 }C$

  2. more than ${ 50 }^{ 0 }C$

  3. less than ${ 50 }^{ 0 }C$ but greater than ${ 0 }^{ 0 }C$

  4. ${ 0 }^{ 0 }C$
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice conduction in metals and non-metals thermal energy transfers physics

When a thermometer is taken from the melting ice to a warm liquid, the mercury level rises to two-fifths of the distance between the lower and the upper fixed points. Find the temperature of the liquid $(i)i{n^o}C,and(ii)\;in\;K.$ 

  1. ${40^0}C.313K$

  2. ${30^0}C.227K$

  3. ${20^0}C.273K$

  4. ${0^0}C.0K$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The Celsius scale has 100 divisions between 0 and 100. Two-fifths of 100 is 40 degrees Celsius. Converting to Kelvin, 40 + 273.15 = 313.15 K, which rounds to 313 K.

Multiple choice conduction in metals and non-metals thermal energy transfers physics

In winter , temprature of bottom of take is 4$$C . Ratio of thermal conductance of ice and water is 2:3 and depth of the take 20 m. Find the maximum thickness os ice formed .  

  1. $\frac { 200 }{ 11 } M$

  2. $\frac { 100 }{ 8 } M$

  3. $\frac { 220 }{ 12 } M$

  4. 10 M
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice conduction in metals and non-metals thermal energy transfers physics

A semicircular rod is joined at its end to a straight rod of the same material and the same cross-sectional area. The straight rod forms a diameter of the other rod. The junctions are maintained at different temperatures. Find the ratio of the heat transferred through a cross-section of the semicircular rod of the heat transferred through a cross-section the straight rod in the given time.

  1. $\dfrac 2\pi$

  2. $\dfrac 1\pi$

  3. $\dfrac 1{2\pi}$

  4. $\dfrac \pi2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Heat flow rate is proportional to cross-sectional area and inversely proportional to length. For a semicircular rod of radius R, the length is pi*R and area is A. For the straight diameter rod, length is 2R and area is A. The ratio of heat flow (H_semi / H_straight) = (K*A*dT / (pi*R)) / (K*A*dT / (2*R)) = 2/pi.

Multiple choice conduction in metals and non-metals thermal energy transfers physics

Bimetallic thermostat consists two metals of different thermal co-efficient thermostat always bends towards material having
(i)large thermal expansion on heating 
(ii)large thermal expansion on cooling
(iii)small thermal expansion on heating
(iv)small thermal expansion on cooling

  1. I only

  2. II only

  3. III and II only

  4. I and IV only
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice conduction in metals and non-metals thermal energy transfers physics

Two angular blocks A and B different metal have same length and same area of cross-section . they are kept in such a way that their cross-sectional area touch each other. the temperature at one end of A is $ 100^0 $ C and that of B at the other end is $0^0 C $ C . if the ratio of their conductivity is 1:3 then under steady state, the temperature of the junction in contact will be:-

  1. $ 25^0 C $

  2. $ 50^0 C $

  3. $ 75^0 C $

  4. $ 100^0 C $
Reveal answer Fill a bubble to check yourself
C Correct answer