- Introduction
- |
- Thermal Conduction
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- Thermal Conductivity
- |
- Convection
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- Radiation
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- Black Body Radiation
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- Stefan Boltzmann law
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- Nature of thermal Radiation
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- Kirchoff's law
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- Newton's Law of Cooling
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- Solved examples

**Multiple choice questions with one or more answers**

**Q-1.** A Cylinder of radius R made of a material having thermal conductivity K is surrounded by a parrallopied having inner hole of radius R and outer dimension of 3 R each. Thermal conductivity of parrallopied is 2K

The effective thermal conductivity of the system

a, K[2 + (π/9)]

b, K[2 + (π)]

c, K[2 - (π/9)]

d, 3 K

**Q-2**. Three black bodies are such that higher intensity wavelengths are in the ratio

λ_{m1} : λ_{m2} : λ_{m3} = 1 :(21)^{1/2}: (3)^{1/2}

which of the these is true for the temperatures

a, T_{1} > T_{3} > T_{2}

b, T_{1} > T_{2} > T_{3}

c, T_{3} > T_{2} > T_{1}

d, T_{3} > T_{1} > T_{2}

**Q-3**

All Rod are of equal length and equal area of cross-section. Find the temperature at point B

a, 45

b, 51.4

c, 50

d, 51

**Q-4**

Three identical rods are connected between two container contained at Temp. T_{1} and T_{2} (T_{1} > T_{2} ) .There are three possible way to join the rod both the container as show below.

Let Q_{1}, Q_{2}, Q_{3} are the rate of heat flow for these three figure respectively

when of these is true.

a, Q_{3} > Q_{2} > Q_{1}

b, Thermal resistance is maximum in fig(a)

c, Q_{1} : Q_{3} = 1 : 9

d, All the above

**Linked comprehension type**

A rod of thermal conductivity K and area A and length L is there. The initial temperature distribution along the rod is given by

T = T_{0} sin (π x / L)

where T_{0} is in ºC. Suppose both the end of the rod kept at 0ºC.

**Q-5** which of these is the initial temperature distribution diagram

a.

b.

c.

d.

**Q-6** What is the initial temperature gradient at the end of rods

a, T_{0} π/L

b, T_{0}π

c, T_{0} / L

d, T_{0}/πL

**Q-7** What is the initial heat current from the ends of the rods into the bodies making contact with its ends

a, πKAT_{0}/L

b, KAT_{0}/L

c, 3KAT_{0}/L

d, 4KAT_{0}/L

**Q-8** What is the initial heat current at the center of rod

a, zero

b, KAT_{0}/L

c, 2KAT_{0}/L

d, 2KAT_{0}/3L

**Multiple choice questions with one or more answers**

**Q-9** Steady state temperature distribution along a rod is shown by which figure.

a.

b.

c.

d.

**Q-10** Which of these is true for a black body

a.(a = 1) , (e = 1)

b, Reflect radiation & refract radiation

c, frequency of radiation which is dominant is directly proportional to the temperature of the body

d, All of the above

**Q-11**

There are two bodies A & B they are having same surface and same mass. They are at temperature T at time t=0

Temperature of the surrounding is T_{0}

Given (T > T_{0})

Let a_{1} & a_{2} are the absorptive power of the two surface and a_{1} > a_{2}

which of these is true

a, Body A will cool faster than body B

b, Emissivity is greater for body B

c, Emissivity is greater for body A

d, Body B will cool faster than body A

**Linked comprehension type**

Two sphere A & B are there of same material

sphere A is hollow sphere

sphere B is solid sphere

Radius is same for both the sphere

They are at same temperature T_{0}

**Q-12**

Two statement are made about the above scenario

A) dT/dt at t = 0 will be same for the sphere

(B) Emissive power of both the sphere will be same in the beginning

(a) A & B both are correct

(b) Only B is correct

(c) Only A is correct

(d) None of them is correct

**Q-13** if the temperature difference between sphere and surrounding is T for both the sphere which one is true

a. A will cool faster for all values of T

b. A & B both will cool at same rate for all values of T

c. A & B will have equal temperature at any instant

d none of the above

**Q-14** if the sphere A radius is doubled then what will be ratio of emissive power of sphere A & B in the beginning

a E_{1}:E_{2}=4:1

b.E_{1}:E_{2}=1:4

c. E_{1}:E_{2}=2:1

d. E_{1}:E_{2}=1:2

**Multiple choice questions with one or more answers**

**Q-15**

A hot body whose temperature is T is kept in a room where temperature is T_{0}.The hot body takes time t_{1} to cool from temperature T to T_{2},time t_{2} to cool from temperature T_{2} to T_{3},time t_{3} to cool from temperature T_{3} to T_{4}

Also T > T_{2} > T_{3} > T_{4} > T_{0}

and T - T_{2}=T_{2} -T_{3}=T_{3}-T_{4}=a

which one of the following is true

a. t_{1}>t_{2}>t_{3}

a. t_{3}>t_{2}>t_{1}

a. t_{1}=t_{2}=t_{3}

d. None of the above

**Q-16** if the temperature of the body is plotted against time which of the following curve will represent it

a.

b.

c.

d.

a E

b.E

c. E

d. E

temperature

a E

b.E

c. E

d. E

Q-20

A composite slab is prepared by pasting three slab of thickness L

a.K

b.K

c. K

d. L

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