3532IES-7. ANS. (C) IES-8. ANS. (C) IES-9. ANS. (C) IES-10. ANS....

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2

IES-7. Ans. (c)

IES-8. Ans. (c)

IES-9. Ans. (c)

IES-10. Ans. (a)

IES-11. Ans. (d)

IES-12. Ans. (d)

IES-13. Ans. (b)

σ

π

2

4

2

4

E

r T

=

∴

=

=

×

=

4

1

4000

4

E

AT

IES-14. Ans. (c)

A

A

A

;

1

(

)

π

4

4

2000

×

B

B B

IES-15. Ans. (a)

4

4

E

T

300

1

εσ

^⎛

^⎞

^⎛

^⎞

4

1

1

=

=

⎜

⎝

⎟

⎠

=

⎜

⎝

⎟

⎠

=

Emissive power ( )

IES-16. Ans. (d)

E

T or

900

81

2

2

IES-17. Ans. (d) Irradiation on a small test surface placed inside a hollow black spherical

chamber = σT

⁴

= 5.67 × 10

^-8

× 600

⁴

= 7348 W/m

²

IES-18. Ans. (a) Rate of emission of radiative flux

=

σ

T

⁴

3

8

4

or

7.35 10

×

=

5.67 10

×

⁻

×

T

or

T

=

600 K

IES-19. Ans. (c)

IES-20. Ans. (b)

Heat transfer through solid

→

Fourier’s law of heat

conduction

Heat transfer from hot surface to

surrounding fluid

→

Newton’s law of cooling

Heat transfer in boiling liquid

→

Convection heat transfer

Heat transfer from one body to

→

Radiation heat

Page 91 of 97

another transfer separated in

space

IES-21. Ans. (a)

IES-22. Ans. (b)

IES-23. Ans. (b)

IES-24. Ans. (d) Total emissive power is defined as the total amount of radiation emitted

by a body per unit time

∫

. .

0 3 150 (12 3) 300 (25 12) 0[ ]

i e

E

=

E d

_λ

λ λ

= × +

×

−

+

×

−

+

α

=

× +

×

=

+

=

150 9 300 13 1350 3900 5250 W/m

IES-25. Ans. (c)

IES-26. Ans. (c)

IES-27. Ans. (b) As per Wien's law,

λ

_{1 1}

T

=

λ

_{2 2}

T or

5800 0.5

×

=

λ

₂

×

573

IES-28. Ans. (c)

IES-29. Ans. (c) We know that, I =

E

IES-30. Ans. (c)

IES-31. Ans. (c) All the emission from one plate will cross another plate. So Shape Factor

in one.

IES-32. Ans. (b) A

1

F

1 – 2

= A

2

F

2 – 1

or

F

2 – 1

=

¹

_{1 2}

A

.

A

F

⁻

=

6

0.1

4

×

= 0.15

IES-33. Ans. (c)

_{2 1}

_{2 2}

_{2 2}

_{2 1}