Physics

Introduction to Thermodynamics

Thermodynamics is the branch of physics that deals with heat, temperature, and their relation to energy and work. It involves laws that describe how energy moves and changes in a system.

Core Concepts

Temperature

A measure of average kinetic energy of particles.

Heat

Energy transferred due to temperature difference.

Internal Energy

Total kinetic and potential energy of particles.

Important Equations

Q = mcΔT

Heat transfer

ΔU = Q - W

First Law

PV = constant

Boyle’s Law

Ideal Gas Law

PV = nRT

Laws of Thermodynamics

Zeroth Law: If A = B and B = C in thermal equilibrium, then A = C.
First Law: Energy can be changed from one form to another, but cannot be created or destroyed.
Second Law: Heat cannot spontaneously flow from colder to hotter body.
Third Law: As temperature approaches absolute zero, the entropy of a system approaches a minimum.

Example Problems

1. Find heat required to raise temperature of 2 kg water by 20°C

Solution: Q = mcΔT = 2 × 4200 × 20 = 168,000 J

2. If Q = 500 J and W = 200 J, what is ΔU?

Solution: ΔU = Q - W = 500 - 200 = 300 J

3. A gas expands isothermally. If P₁V₁ = P₂V₂, find V₂

Solution: V₂ = P₁V₁ / P₂