JEE Main202228 Jul 2022Evening ShiftPhysicsUnits and DimensionsActual
Consider the efficiency of Carnot's engine is given by η = α β sin θ log e β x k T , where α and β are constants. If T is temperature, k is Boltzman constant, θ is angular displacement and x has the dimensions of length. Then, choose the incorrect option.
Options
- ADimensions of β is same as that of force.
- BDimensions of α - 1 x is same as that of energy.
- CDimensions of η - 1 sin θ is same as that of α β
- DDimensions of α is same as that of β
Correct answer
D. Dimensions of α is same as that of β
Step-by-step solution
Given that, η = α β sin θ log β x k T . Since expression inside the logarithm is dimensionless β x = k T Since the dimensions of k T are equivalent to that of energy, β = k T x = E x = ML 2 T - 2 L = MLT - 2 Therefore, β has dimensions of force. Since efficiency is a dimensionless ratio, α β = M 0 L 0 T 0 ⇒ β = 1 α Therefore, dimensions of α is not same as that of β . Hence option D is incorrect statement and the answer. x α = β x