list of physics formulas class 11 chapter Transmission of Heat

Physics Formulas

Class - 11 Chapter Transmission of Heat 

Coefficient of Thermal conductivity:

In steady state the quantity of heat Q flowing through a metal rod of length l and cross-section A in a time. t when its ends are at temperature θ1, and θ2  (θ1, θ₂) is given by

thermal conductivity

where K is coefficient of thermal conductivity

  • K depends on the nature of the metal.
  • It is defined as the rate of flow of heat per unit area and per unit temperature gradient in steady state.
  • If one end of a metal rod is kept in a steam jacket and other end is kept in an ice block, then the amount of ice that melts is 

metal rod

Junction temperature

In steady state when conduction takes place through two layers of composite wall with different thermal conductivities, then

junction temperture

Thermal Resistance R

Thermal resistance R of a conductor of length l, cross-section A and conductivity K is given by

R = 1/KA

Effective conductivity:

  • Series combination: If two rods of same cross-sectional area having lengths l1 and l2 and conductivities K1 and K2 are connected in series, then in steady state conductivity of the combination K is given by

series combination

  • Parallel combination: If two rods of same length having cross sectional area A1, A2 and conductivities K1, K2 are arranged in parallel, then in steady state, the conductivity of the combination is

parallel combination

Emissive Power:

  • The amount of energy emitted per second per unit surface area of a body at a given temperature for a given wave –length range (λ and λ + dλ) is called emissive power.
  • At a given temperature if the radiations emitted have a wave length difference dλ, then the emissive power is equal to eλdλ.
  • S.I unit of emissive power is Wm–2 and its dimensional formula is MT–3.


The ratio of radiant energy emitted by a surface to radiant energy emitted by a black body under same conditions is called emissivity. For a perfect black body emissivity e = 1

Do follow NCERT Solutions for Class 11 Physics prepared by expert faculty of Physics Wallah. 


Download the Pdf of class 11 physics formula sheet of chapter Transmission of Heat from the link given below 

list of physics formulas class 11 chapter Transmission of Heat

list of physics formulas class 11 chapter Transmission of Heat

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