Heat and Thermodynamics

General Overview

1. Thermal expansion is the tendency of materials to expand or contract with changes in temperature.
2. It is a crucial factor in the design of various structures and devices to prevent damage or failure.
3. The phenomenon is applied in engineering, construction, and daily life to ensure safety and functionality.

Applications in Railway Tracks

1. Railway tracks are made of steel, which expands during hot weather and contracts during

General Overview

1. Thermal expansion refers to the increase in the size (length, area, or volume) of a material due to an increase in temperature.
2. The extent of expansion depends on the material properties and the degree of temperature change.
3. The coefficient of expansion is a measure of how much a material expands per degree change in temperature.

Coefficient of Linear Expansion

1. The coefficient of linear expansion (α) describes the change

General Concepts of Thermal Expansion

1. Thermal expansion is the increase in the size (length, area, or volume) of a substance when its temperature is increased.
2. It occurs due to an increase in the kinetic energy of particles, which increases the separation between them.
3. Thermal expansion is observed in solids, liquids, and gases.
4. The degree of expansion depends on the material properties and the amount of temperature change

Heat Engines

1. A heat engine is a device that converts heat energy into mechanical work.
2. It operates between a hot reservoir and a cold reservoir.
3. The working principle is based on the First and Second Laws of Thermodynamics.
4. The efficiency of a heat engine is given by η = W/Q₁, where:
   • W is the work output.
   • Q₁ is the heat absorbed from the hot reservoir.

Entropy

1. Entropy is a measure of the disorder or randomness of a system.
2. The symbol for entropy is S, and its SI unit is joules per kelvin (J/K).
3. It quantifies the unavailability of a system's energy to perform useful work.
4. The Second Law of Thermodynamics states that entropy always increases in a spontaneous process.
5. ΔS = Q/T, where:
   • ΔS is the change in entropy.
   • Q is the heat exchanged.

Zeroth Law of Thermodynamics

1. The Zeroth Law of Thermodynamics defines the concept of thermal equilibrium.
2. If two systems are each in thermal equilibrium with a third system, they are in thermal equilibrium with each other.
3. This law provides the foundation for the definition of temperature.
4. Thermometers work based on the Zeroth Law.

First Law of Thermodynamics

1. The First Law of Thermodynamics is a statement of the conservat

1. Thermal conductivity is a material's ability to conduct heat.
2. It is denoted by the symbol k or λ.
3. The SI unit of thermal conductivity is watt per meter per kelvin (W/m·K).
4. Fourier's Law describes heat conduction: Q = -kA(dT/dx), where:
   • Q is the heat transfer rate.
   • k is the thermal conductivity.
   • A is the cross-sectional area.
   • dT/dx is the temperature gradient.

1. Heat transfer is the movement of thermal energy from a region of higher temperature to a region of lower temperature.
2. There are three primary modes of heat transfer: conduction, convection, and radiation.

Conduction

1. Conduction is the transfer of heat through a material without the movement of the material itself.
2. It occurs mainly in solids, where particles are tightly packed.
3. The rate of conduction is described by Fourier’s Law: Q = -kA(dT/dx)

1. Heat capacity is the amount of heat energy required to raise the temperature of a body by 1 degree Celsius or Kelvin.
2. The SI unit of heat capacity is joule per kelvin (J/K).
3. Specific heat capacity is the amount of heat energy required to raise the temperature of 1 kilogram of a substance by 1 degree Celsius or Kelvin.
4. The formula for specific heat capacity is c = Q / (m × ΔT), where:
   • Q is the heat energy supplied.
   • m is the mass of the substance.

1. Temperature is a measure of the average kinetic energy of the particles in a substance.
2. Heat is the transfer of thermal energy between systems due to a temperature difference.
3. There are three primary temperature scales used in thermodynamics: Celsius, Fahrenheit, and Kelvin.
4. The Celsius scale (°C) is widely used in most parts of the world and in scientific work.
5. In the Celsius scale, the freezing point of water is 0°C an