RBSE Class 11 Physics Notes Chapter 11 Thermal Properties of Matter

These comprehensive RBSE Class 11 Physics Notes Chapter 11 Thermal Properties of Matter will give a brief overview of all the concepts.

RBSE Class 11 Physics Chapter 11 Notes Thermal Properties of Matter

→ Temperature is relative measurement of hotness or coldness. The SI unit of temperature is Kelvin (K).

→ Heat flows from an object from higher temperature to another at lower temperature.

→ The SI unit of heat is Joule.

→ Thermometer is used to measure temperature.

→ The conversion relation between different temperature scales can be written as:
\(\frac{C}{100}=\frac{F-32}{180}=\frac{R}{80}=\frac{K-273}{100}\)

→ The coefficient of linear expansion,
α = \(\frac{\Delta l}{l_0} \times \frac{1}{\Delta T}\)

The areal expansion
β = \(\frac{A}{A_0} \times \frac{1}{\Delta T}\)
β = 2α

The coefficient of volume expansion,
γ = \(\frac{\Delta V}{V} \times \frac{1}{\Delta T}\)
γ = 3α

 

→ Specific heat of a substance is the amount of heat energy needed to raise the temperature of unit mass of a substance through 1°C.

→ Melting Point:
The temperature at which solid and liquid state of a substance co-exist.

→ Boiling Point:
The temperature at which liquid and gaseous state of a substance co-exist.

→ Sublimation:
The process of change of solid into gaseous state or vice-versa without passing through the liquid state.

→ Thermal expansion refers to the expansion in a dimension (length or volume) of a body.

→ Triple point:
Triple point of a substance is the point where all the three states of the substance (i.e., solid, liquid and gas) co-exist.

→ Conduction:
In this mode of heat transfer, heat is transferred without the actual movement of molecules.

→ Convection:
It is the process by which heat is transferred in a system from one point to another due to motion of the heated particles of the system.

→ Radiation:
It is the process by which heat is transferred from one mass to another, without heating the medium (if any).

→ Newton’s Law of Cooling:
The rate of loss of heat of a body is directly proportional to the difference of temperature of the body and surroundings.

→ Black Body:
A body which absorbs whole (almost) amount of radiant energy incident on it.

→ Wien’s Displacement Law:
λ_mT = b = constant

→ Stefan’s Law:
The total energy emitted by a black body per second per unit area is directly proportional to the fourth power of temperature, i.e.,
E_b ∝ T⁴
or E_b = σT⁴
where σ = Stefan’s constant.

→ Relation between different temperature scales,
\(\frac{C}{5}=\frac{R}{4}=\frac{F-32}{9}=\frac{K-273}{5}\)

→ Linear coefficient of expansion,
α = \(\frac{\Delta l}{l_0 \Delta T}\)

→ The areal expansion
β = \(\frac{\Delta A}{A_0 \Delta T}\)

→ Volume coefficient of expansion,
β = \(\frac{\Delta V}{V \Delta T}\)

→ Relation between p and a
β = 2α
γ = 3α

→ Specific heat, s = \(\frac{\Delta Q}{m \Delta T}\)

→ Heat absorbed during increase in temperature
ΔQ = msΔT

→ Heat absorbed during phase change
ΔQ = mL

→ Law of thermometry,
Heat absosbed = Heat lost

→ Relation between reflection coefficient, absorption coefficient and transmission coefficient
r + α + t = 1

→ Quantity of heat during conduction
ΔQ = \(\frac{K A \Delta T}{L}\)dt

→ Thermal current H = \(\frac{d Q}{d t}=\frac{K A \Delta T}{L}\)

→ Newton’s law of cooling ‘
(i) -\(\frac{d Q}{d t}\) = k(T - T₀) and
(ii) = \(\frac{d T}{d t}=\frac{-k}{m s}\) (T - T₀)
\(\frac{k}{m x}\) = K
∴ \(\frac{d T}{d t}\) = -K(T - T₀)

→ Relative emissivity, ε = \(\frac{e_\lambda}{E_\lambda}\)

→ Total emissive power, e_T = \(\int_0^{\infty}\)e_λ dλ

→ Kirthhofl’s law, \(\frac{e_\lambda}{a_\lambda}\) = E_λ (constant)

→ Wien’s displacement law
λ_mT = b (i constant)

→ Stefan’s law E = σT⁴
and \(\frac{d Q}{d t}=\frac{\sigma E A}{J}\left(T^4-T_0^4\right)\)

→ Temperature: It is the degree of hotness of a body. The temperature of a body gives a measure of the average kinetic energy of its molecules.

→ Specific heat: It may be defined as the amount of heat required to raise the temperature of unit mass of a substance through one degree.

→ Molar specific heat: It is defined as the amount of heat required to raise the temperature of 1 mole of the substance through one degree.

→ Heat capacity: It is defined as the amount of heat required to raise the temperature of a body through one degree.

→ Water equivalent: The water equivalent of a body is defined as the mass of water which requires the same amount of heat as is required by the given body for the same rise of temperature.

→ Latent heat: The amount of heat required to change the state of unit-mass of a substance at a constant temperature is called its latent heat.

→ Steady stqte: The state of the rod when temperature of every cross-section of the rod becomes constant and there is no further absorption of heat in any part is called steady state.

→ Emissivity: It is the ratio of the emissive power of a body (e) to the emissive power (E) of a black body at the same temperature.

→ Solar constant: It is defined as the amount of solar radiant energy that a unit area of a perfect black body on the earth would receive per second in the absence of the atmosphere, with its surface perpendicular to the direction of the sun rays. Its value is 1340 W/m².