Thermal Propertie, Thermodynamics And Kinetic Theory

Question 1

The length, area and volume of a solid increases with temperature as

Answer 1

• L = L₀ (1 + αt)
• A = A₀ (1 + βt)
• V = V₀ (1 + γt)

α: coeff of linear expansion
β: coeff of superficial expansion
γ: coeff of cubical expansion

Question 2

For small change in temp, ∆L, ∆A, ∆V

Answer 2

• ∆L = Lα∆T
• ∆A = Aβ∆T
• ∆V = Vγ∆T

Question 3

Effect of temp on time period of pendulum

Answer 3

∆T/T = ½α∆t

• ∆t - temp diff
• ∆T - time period diff

Question 4

Types expansion in solids

Answer 4

• linear expansion
• areal expansion
• volume expansion

Question 5

Thermal expansion of liquids

Answer 5

γᵣₑₐₗ = γₐₚₚₐᵣₑₙₜ + γ꜀ₒₙₜₐᵢₙₑᵣ

γᵣₑₐₗ = γₐₚₚₐᵣₑₙₜ + 3αᵥₑₛₛₑₗ

Question 6

What is specific heat

Answer 6

Heat required to raise the temp or unit mass of a substance through 1°C or 1K

Question 7

Heat capacity of water

Answer 7

• 4200 J/kgK
• 1cal/gm°C

Question 8

Principle of calorimetry

Answer 8

Heat lost by hot body = heat gained by cold body

• m1C(T1 - T) = m2C(T - T2)

m1: mass of first body
m2: mass of second body
T1: temp of first body
T2: temp of second body

Question 9

What is thermal capacity

Answer 9

Amount of heat required to raise the temp of a body by 1°C
- thermal capacity= mass × specific heat

Question 10

Cp and Cv relation

Answer 10

• Cp - Cv = R
• Cp/Cv = 1 + 2/f = γ

f: degrees of freedom

Question 11

What is latent heat

Answer 11

Amount of heat required to change the state of unit mass of the substance

Question 12

Latent heat of ice

Answer 12

80cal/g

Question 13

Latent heat of steam

Answer 13

540 cal/g

Question 14

Rms velocity of gas

Answer 14

V = √ (3RT/M)

Question 15

Average speed of gases

Answer 15

V avg = √ (8RT/πM)

Question 16

Most probable speed of gas

Answer 16

V = √ (2RT/M)

Question 17

Mean free path

Answer 17

λ = 1/ √2 πd²n

d: diameter of molecule
n: no: or molecules per unit volume

Question 18

Pressure exerted by gas

Answer 18

P = ⅓ρV²

P: pressure
ρ: density
V: rms velocity

Question 19

V and P for an ideal gas

Answer 19

At const temp for a given mass of ideal gas (Boyle’s law)
V ∝ 1/P

Question 20

At what temp celcius and fahrenheit are same?

Answer 20

40°

Question 21

Thermal conductivity of slabs in parallel (which have same dimensions)

Answer 21

K = (K₁ + K₂) / 2

Question 22

Thermal conductivity of slabs in series (which have same dimensions)

Answer 22

K = 2k₁k₂ / (k₁ + k₂)

Question 23

Newton’s law of cooling

Answer 23

(θ₁ - θ₂) /t ∝ [ (θ₁+θ₂)/2 ] - θs

• θ₁: initial temp of body
• θ₂: final temp of body
• t: time taken to cool from θ₁ to θ₂
• θs: temp of surroundings