Calorimetry And Heat Transfer.

Question 1

What is the formula of q when temperature changes without change in state ?

Answer 1

Q= msΔ#

Question 2

What is the formula for q when state changes without change in temperature ?

Answer 2

Q=mL, when state changes without change in temperature.

Question 3

What is meant by specific heat of a substance s?

Answer 3

Specific heat of a substance s is the heat required to increase the temperature of unit mass by 1 C or 1K

Question 4

What is the heat capacity of the body ?

Answer 4

Heat capacity of a body= ms= heat required to increase the temperature of whole body by 1 C or 1K

Question 5

What is latent heat of a substance ?

Answer 5

Latent hey of a substance L is the heat required to convert unit mass of the substance from one state to another state.

Question 6

What is meant by water equivalent of a vessel ?

Answer 6

Water equivalent of a vessel of the mass equivalent of water which takes same amount of heat as taken by the vessel for same rise of temperature.

Question 7

What is absorptive power a ?

Answer 7

Absorptive power a = energy absorbed / energy incident.

a

Question 8

What is spectral absorptive power aλ?

Answer 8

Spectral absorptive power aλ= Absoptive power of wavelength λ.
aλ

Question 9

What is emissive power e ?

Answer 9

Emissive power e is the energy radiate per unit area per unit time. It’s SI units are joule per second per metre square.

Question 10

What is Stephans Law?

Answer 10

Emissive power of a body is given by e= e(r)σT⁴Αt.

A= Surface Area. t= time.

Question 11

What is Kirchhoff’s Law?

Answer 11

If different bodies (including a perfectly black body) are kept at same temperature then,
e(λ)/a(λ)=constant.

Question 12

What are the two conclusions that can be drawn from Kirchhoff law?

Answer 12

1. Good absorbers are good emitters ( for a particular wavelength ).
2. Ratio (λ)/a(λ)=constant, at any given temperature. This ratio is equal to e(λ) of a perfectly black body at that temperature.

Question 13

What is the formula of weins displacement law ?

Answer 13

λ(m)T=b
b=Weins constant= 2.89 x 10^-3. Further area of graph of e(λ) vs λ will give total emissive power which is proportional to T⁴.

Question 14

What is Newtons Law of cooling?

Answer 14

Newtons law of cooling states that if temperature difference of a body with atmosphere is small, then rate of cooling is directly proportional to temperature difference.

Question 15

What is the formula of Newtons Law of Cooling ?

Answer 15

(#₁−#₂/t)=α[((#₁+#₂)/2) - #₀]