Q KA T= ( 1−T2)CODES

5.

q kA T

=

(

1

−

T

2

)

Codes:

A B C D A B C D

Page 81 of 97

(a)

4

1

3

2

(b)

4

5

1

2

(c)

2

1

3

4

(d)

2

5

1

4

IES-22. Match List-I (Law) with List-II (Effect) and select the correct answer

using the code given below the lists:

[IES-2008]

List-I

List-II

A. Fourier's Law

1. Mass transfer

B. Stefan Boltzmann Law

2. Conduction

C. Newton's Law of Cooling

3. Convection

D. Ficks Law

4. Radiation

Codes:

A

B

C

D

A

B

C

D

(a)

3

1

2

4

(b)

2

4

3

1

(c)

3

4

2

1

(d)

2

1

3

4

Planck's Law

IES-23. What is the basic equation of thermal radiation from which all other

equations of radiation can be derived?

[IES-2007]

(a) Stefan-Boltzmann equation

(b) Planck’s equation

(c) Wien’s equation

(d) Rayleigh-Jeans formula

IES-24. The spectral emissive power E

λ

for a diffusely emitting surface is:

E

λ

= 0

for λ< 3 μm [IES-1998]

E

λ

= 150 W/m

²

μm

for 3 < λ < 12 μm

E

λ

= 300 W/m

²

μm

for 12 < λ < 25 μm

E

λ

= 0

for λ > 25 μm

The total emissive power of the surface over the entire spectrum is:

(a) 1250 W/m

²

(b) 2500 W/m

²

(c) 4000 W/m

²

(d) 5250 W/m

²

IES-25. The wavelength of the radiation emitted by a body depends upon

(a) The nature of its surface

(b) The area of its surface

[IES-1992]

(c) The temperature of its surface

(d) All the above factors.

Wien Displacement Law

IES-26. Match List-I with List-II and select the correct answer using the code

given below the lists:

[IES-2005]

A. Radiation heat transfer

1. Fourier number

B. Conduction heat transfer

2. Wien displacement law

C. Forced convection

3. Fourier law

D. Transient heat flow

4. Stanton number

Codes:

A

B

C

D

A

B

C

D

(a)

2

1

4

3

(b)

4

3

2

1

(c)

2

3

4

1

(d)

4

1

2

3

IES-27. Sun's surface at 5800 K emits radiation at a wave-length of 0.5 μm. A

furnace at 300°C will emit through a small opening, radiation at a

wavelength of nearly

[IES-1997]

(a)

10

μ (b)

5

μ (c)

0.25

μ (d)

0.025

μ

Page 82 of 97

Intensity of Radiation and Lambert's Cosine Law

IES-28. Which one of the following statements is correct?

[IES-2007]

For a hemisphere, the solid angle is measured

(a)

In radian and its maximum value is π

(b)

In degree and its maximum value is 180°

(c)

In steradian and its maximum value is 2 π

(d)

In steradian and its maximum value is π

IES-29. Intensity of radiation at a surface in perpendicular direction is equal

to:

[IES-2005; 2007]

(a) Product of emissivity of surface and 1/π

(b) Product of emissivity of surface and π

(c) Product of emissive power of surface and 1/ π

(d) Product of emissive power of surface and π

IES-30. The earth receives at its surface radiation from the sun at the rate of

1400 W/m

²

. The distance of centre of sun from the surface of earth is