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Notes : Thermal Equilibrium: Adiabatic & Diathermic Walls | Class 11 Physics 1. Defining Thermal Equilibrium The concept of equilibrium has different meanings in mechanics and thermodynamics. Mechanical Equilibrium A system is said to be in mechanical equilibrium when the net external force and the net torque acting on it are zero. This condition is related to motion, forces, and balance. Thermodynamic Equilibrium A system is said to be in thermodynamic equilibrium if the macroscopic variables that characterize the system do not change with time. Macroscopic Variables Include: Pressure (P) Volume (V) Temperature (T) Mass Composition Example Consider a gas enclosed in a closed, rigid container that is completely insulated from its surroundings. If its pressure, volume, temperature, mass, and composition remain constant with time, the gas is said to be in a state of thermodynamic equilibrium. 2. Influence of Boundary Walls Whethe...

Internal Energy, Heat and Work 1. Internal Energy (U) Internal energy is the total microscopic energy possessed by a thermodynamic system. Definition It is the sum of: Kinetic Energy of molecules due to: Translational motion Rotational motion Vibrational motion Potential Energy due to intermolecular forces between molecules. Therefore, U =  Total Molecular Kinetic Energy + Total Molecular Potential Energy Important Points Internal energy includes only the random microscopic motion of molecules. It does not include the kinetic energy of the entire system moving as a whole. It is measured in a frame where the centre of mass of the system is at rest . Example: A gas inside a cylinder possesses internal energy due to molecular motion. If the cylinder is thrown upward, the kinetic energy of the moving cylinder is not part of its internal energy. State Variable Internal energy is a state function (state variable...

Zeroth Law of Thermodynamics The Zeroth Law of Thermodynamics is the most fundamental law of thermodynamics. It introduces the concept of temperature and provides the basis for measuring temperature. The law explains thermal equilibrium and forms the foundation of all temperature-measuring devices. Introduction In everyday life, we compare objects by saying that one object is hotter or colder than another. To make this comparison scientifically, we need a measurable quantity called temperature . The Zeroth Law of Thermodynamics provides the scientific basis for defining temperature. Statement of Zeroth Law If two thermodynamic systems are separately in thermal equilibrium with a third system, then they are in thermal equilibrium with each other. In simple words, if System A has the same temperature as System C, and System B also has the same temperature as System C, then Systems A and B must have the same temperature. Thermal Equilibrium Thermal equilibrium is the ...

Second Law of Thermodynamics – Definition, Statements, Limitations, FAQ & Quiz The Second Law of Thermodynamics is one of the most important laws of physics. While the First Law explains the conservation of energy, the Second Law explains the direction of natural processes and the limitations on the conversion of heat into work. Need for the Second Law of Thermodynamics The First Law of Thermodynamics states that energy can neither be created nor destroyed. However, it does not tell us whether a process can occur naturally or not. For example, a book lying on a table could theoretically absorb heat from the table and convert that heat completely into mechanical energy to jump upward. Such a process would satisfy the First Law because energy is conserved. But such a process never occurs in nature. Therefore, another law is needed to determine which processes are possible and which are impossible. This requirement leads to the Second Law of Thermodynamics. Limitat...

Thermodynamics – Introduction 1. Introduction In the previous chapter, we studied the thermal properties of matter. In this chapter, we study the laws governing thermal energy and the conversion of heat into work and vice versa. Examples of Heat and Work Conversion Rubbing of Palms: In winter, when we rub our palms together, the work done against friction produces heat and our hands become warm. Steam Engine: In a steam engine, the heat energy of steam is used to do useful work in moving the piston, which rotates the wheels of the train. Energy Conversion: \[ \text{Work} \rightarrow \text{Heat} \] \[ \text{Heat} \rightarrow \text{Work} \] 2. Historical Concept of Heat In physics, concepts like heat, temperature and work must be defined carefully. Historically, it took a long time to understand the true nature of heat. Caloric Theory of Heat According to the old caloric theory, heat was regarded as a fine invisible fluid called caloric present insid...

Notes : Chapter 11 Thermodynamics Class 11 Physics - Physicskund  11.1 Introduction 11.2 Thermal equilibrium 11.3 Zeroth law of Thermodynamics 11.4 Heat, internal energy and work 11.5 First law of thermodynamics 11.6 Specific heat capacity 11.7 Mayer Formula proof 11.8 Thermodynamic state variables and equation of state 11.9 Thermodynamic processes 11.10 Second law of thermodynamics 11.11 Reversible and irreversible processes 11.12  Carnot engine

Definition of Refraction of light : The change in direction of light when it passes from one medium to another obliquely is called refraction of light . In other words , the bending of light when it goes from one medium to another obliquely is called Refraction of light. Important terms Related to Refraction: The plane surface that refracts light is known as the surface of refraction. Point of incidence: The point on the surface of refraction , where the ray of light is incident is known as the point of incidence . "O" is the point of incidence. Incident Ray : The ray of light which strikes the surface of refraction at the point of incidence , is known as the incident Ray . AO is the incident Ray. Refracted ray : The ray which travels from the point of incidence to other medium is known as the refracted ray. OB is the refracted ray. Normal : Perpendicular drawn on the surface of refraction at the point of incidence is called normal. NON' is the normal on the surface PQ. A...