Ch 12Thermodynamics — Class 11 Physics, concept-first.

Thermodynamics is the branch of physics that studies the laws governing thermal energy — the conversion of work into heat and heat into work.

The idea of equilibrium is central to thermodynamics. A system is said to be in thermal equilibrium when its macroscopic properties — temperature, pressure, volume — do not change with time, and there…

Before the Zeroth Law can be stated, you need a clear picture of what "thermal equilibrium" means. Two systems are in thermal equilibrium when they are separated by a diathermic wall — a wall that all…

Thermodynamics studies how energy moves and changes form. At its heart lie three quantities that are intimately connected: heat (), internal energy (), and work ().

The first law of thermodynamics is the law of conservation of energy applied to thermodynamic systems. It states that energy can neither be created nor destroyed; it can only change forms.

When you heat a substance, its temperature rises. But the amount of temperature rise for a given amount of heat depends on the substance itself.

A thermodynamic system is described by certain measurable quantities called state variables. These are properties that depend only on the current state of the system, not on how it reached that state.…

A thermodynamic process is any change that a thermodynamic system undergoes — a change from one equilibrium state (initial state) to another equilibrium state (final state).

In thermodynamics, we often want to study how a system changes from one equilibrium state to another. The simplest way to think about this is a sudden, violent change — like a gas expanding explosivel…

An isothermal process is a thermodynamic change that takes place at a constant temperature. The word itself comes from the Greek: iso (equal) and therme (heat).

An adiabatic process is one in which no heat flows between the system and its surroundings. The word comes from Greek — adiabatos meaning "impassable" — and it describes a wall that heat cannot cross.

When a thermodynamic system undergoes a change while its volume remains strictly constant, the process is called isochoric (from Greek isos = equal, chora = space).

An isobaric process is a thermodynamic change that takes place at a constant pressure. The word itself comes from the Greek isos (equal) and baros (weight or pressure).

A thermodynamic process is called cyclic when the system, after undergoing a series of changes, returns exactly to its initial state.

The first law of thermodynamics tells us that energy is conserved in every process. But it says nothing about which processes can actually happen.

In thermodynamics, a process is the path a system takes from one equilibrium state to another. But not all paths are equal.

The central question of practical heat-engine design is this: given a hot reservoir at temperature and a cold reservoir at , what is the maximum possible efficiency, and what cycle of processes achiev…

- Zeroth Law: If and are each in thermal equilibrium with , then and are in thermal equilibrium with each other. This defines temperature as a measurable property.

1. The temperature of an object depends on its average internal energy — the random, microscopic motion of its atoms and molecules.

Higher-order thinking / exemplar-style practice problems.