Transmission

Question 1

Rate of heat flow

Answer 1

/\Q/ /\t = KA/\T /l

Question 2

Unit of thermodynamics constant K

Answer 2

Wm-1K-1

Question 3

Convection

Answer 3

Is the transfer of heat by actual motion of matter

Question 4

Carriers of radiant energy

Answer 4

Electromagnetic waves

Question 5

Absorptive power (a)

Answer 5

a = energy absorbed/ energy incident

Question 6

For a perfect black body a =

Answer 6

1

Question 7

For a perfect black body integral of specific absorptive power

Answer 7

=a

Question 8

Emissive power (e)

Answer 8

e= (/\Q/ /\t)/A

Question 9

Emissivity

Answer 9

It’s the ratio of emissive power of a body to the emissive power of a perfectly black body

Question 10

Amount of heat incident =

Answer 10

Qabsorbed + Qrelflected + Qtransmitted

Question 11

absorptivity

Answer 11

a= Qa/Qi

Question 12

Reflectivity

Answer 12

r = Qr/Qi

Question 13

Transitivity

Answer 13

t= Qt/Qi

Question 14

No material body is

Answer 14

Perfectly black

Question 15

Nearly perfect black body

Answer 15

Platinum and lamp black

Question 16

Kirchhoff’s Law (heat)

Answer 16

Ratio of a to e is always constant and is equal to emitivity of black body

a/e = E=constant

Question 17

Stefan-Boltzmann Law

Answer 17

Energy radiated ~ T^4

E = sigma X AT^4 (for black body)

Else : E = sigma X eAT^4

Where sigma-stefan’s constant = 5.67 X 10^-8 Wm-2K-4

Question 18

Wien’s Displacement Law

Answer 18

Wavelength ~ 1/T

Wavelength X T = constant = b

Where b is Wien’s constant = 2.89 X 10^-3 mK

Question 19

Newtons Law of cooling

Answer 19

Rate of cooling of a body ~ temp. Difference between the body and its surroundings

Question 20

Newtons law of cooling is a special case of

Answer 20

stefan’s law provided temp. Difference is small enough

Question 21

Mathematical form of Newtons law of cooling

Answer 21

dT/dt = k(T1T2/2 -To)

Question 22

Wiedmann and Franz Law

Answer 22

K/conductivity = constant

Question 23

Lorentz extension

Answer 23

K/conductivity xT = constant