INME IN ALL DIRC D B CODES

4. In

me in all dir

C

D

B

Co

des: A

C D

A

B

C

(a)

2

3

4

4

1

3

(b)

3

2

1

4

3

2

4

1

(d)

3

3

1

(c)

2

ES-12. Co

IE

ram

he diagr

nsider t

Which on

e of

giv

the

ven above.

g is correct

t?

e following

s for gray b

(a)

Curve A is

ody,

Curve B is

for black b

and Curv

ve C is

for

mitter.

selective em

Curve A i

(b)

ctive

is for selec

for

emitter, C

ve C

black body

y, and Curv

is for grey b

body.

dy, and Curv

[I

IES-2007]

Curve A is

for grey bod

ve C is for

ve emitter, C

Curve B is f

(c)

for selectiv

.

ve B is for

e C is for

grey body,

, and Curv

(d)

body, Curv

s for black

mitter.

ES-13. Ass

nted black

ane is pain

): The nose

sertion (A)

. [I

ch is gene

IES-1996]

e of aeropla

Black body

y absorbs

m heat whi

Re

ason (R) B

erated by

maximum

c heating w

ing.

plane is flyi

when the p

aer

rodynamic

(a)

(b)

ue and R is t

n of A

the correct e

Both A and

vidually tru

d R are indiv

explanation

rect explana

ue but R is n

ation of A

not the corr

A is true bu

ut R is false

e

but R is true

A is false b

tzmannn Law he StefTfan-Bol

of same m

ES-14. Tw

have radii

material h

s A and B

1 m and

4 m and

wo spheres

nd 2000 K r

[I

tem

mperature

y

espectivel

IES-2004]

4000 K an

hich one of

wing statem

Wh

f the follow

orrect?

ments is co

he energy r

Th

(a)

radiated by

A is:

y sphere A

an that of s

Greater th

phere B

ess than tha

at of sphere

(b) Le

B

hat of spher

Equal to th

(d) Eq

ble that of s

e B

qual to doub

sphere B

IES-15. A body at 500 K cools by radiating heat to ambient atmosphere

maintained at 300 K. When the body has cooled to 400 K, the cooling

rate as a percentage of original cooling rate is about.

[IES-2003]

(a) 31.1

(b) 41.5

(c) 50.3

(d) 80.4

IES-16. If the temperature of a solid state changes from 27°C to 627°C, then

emissive power changes which rate

[IES-1999; 2006]

(a) 6 : 1

(b) 9 : 1

(c) 27 : 1

(d) 81: 1

IES-17. A spherical aluminium shell of inside diameter 2 m is evacuated and

used as a radiation test chamber. If the inner surface is coated with

carbon black and maintained at 600 K, the irradiation on a small test

surface placed inside the chamber is:

[IES-1999]

(Stefan-Boltzmann constant σ = 5.67 × 10

^-8

W/m

²

K

⁴

)

(a) 1000 W/m

²

(b) 3400 W/m

²

(c) 5680 W/m

²

(d) 7348 W/m

²

IES-18. A large spherical enclosure has a small opening. The rate of emission of

radiative flux through this opening is 7.35 kW/m

²

. The temperature at

the inner surface of the sphere will be about (assume Stefan Boltzmann

constants σ = 5.67 × 10

^-8

W/m

²

K

⁴

) [IES-1998]

(a) 600 K

(b) 330 K

(c) 373 K

(d) 1000 K

Kirchoff's Law

IES-19. What is the ratio of thermal conductivity to electrical conductivity

equal to?

[IES-2006]

(a) Prandtl number

(b) Schmidt number

(c) Lorenz number

(d) Lewis number

IES-20. Match List-I with List-II and select the correct answer using the code

given below the lists:

[IES-2008]

List-I

List-II

A. Heat transfer through solid

1. Radiation heat transfer

B. Heat transfer from fluid

2.

Fourier's law of heat

conduction

C. Heat transfer in boiling liquid

3. Convection heat transfer

D. Heat transfer from one body to another

4. Newton's law of cooling

body separated in space

Codes:

A

B

C

D

A

B

C

D

(a)

3

1

2

4

(b)

2

4

3

1

(c)

2

1

3

4

(d)

3

4

2

1

IES-21. Match List-I with List-ll and select the correct answer using the codes

given below the lists:

[IES-1999]

A. Stefan-Boltzmann law

1.

q = hA (T

1

– T

2

)

B. Newton's law of cooling

2.

E =

α

E

_b

q

kL

T

T

C. Fourier's law

3.

(

1

2

)

=

A

−

D. Kirchoff’s law

4.

q

=

σ

A T

(

1

⁴

−

T

2

⁴

)