PhysicsKund Physics class 9 to 12 NCERT, JEE - NEET

Thermodynamic State Variables and Equation of State Every equilibrium state of a thermodynamic system is completely described by a set of macroscopic quantities known as Thermodynamic State Variables or State Functions . What are Thermodynamic State Variables? State variables are measurable physical quantities that define the state of a thermodynamic system when it is in thermodynamic equilibrium. For a gas, the common state variables are: Pressure ($P$) Volume ($V$) Temperature ($T$) Mass ($M$) Number of moles ($\mu$) These variables completely describe the equilibrium state of the system. Condition for State Variables State variables can only be assigned meaningful values when the system is in a state of thermodynamic equilibrium. In equilibrium: Temperature is uniform throughout the system. Pressure is uniform throughout the system. No net macroscopic changes occur with time. Non-Equilibrium States When a system changes rapidly, pressure and temper...

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

Ncert Solution CBSE Class 11 Physics Chapter 7 Gravitation 7.1 Answer the following : (a) You can shield a charge from electrical forces by putting it inside a hollow conductor.Can you shield a body from the gravitational influence of nearby matter by putting it inside a hollow sphere or by some other means ? Solution: You cannot shield a body from the gravitational influence of nearby matter by any means. It is because the gravitational force on a body due to nearby matter is not altered due to the presence of other bodies. In other words , gravitational field cannot be shielded by any means. (b) An astronaut inside a small space ship orbiting around the earth cannot detect gravity. If the space station orbiting around the earth has a large size, can he hope to detect gravity ? Solution: Yes , If the size of the spaceship orbiting earth is very large , an astronaut in it can detect the gravity. (c) If you compare the gravitational force on the earth due to the sun to that due to the ...

Notes : Ncert Class 11 Physics Chapter 5 Work , Energy and Power  1.  Scalar product or dot product of two vectors : 2. Expression for the angle between two vectors 3. Projection of a Vector Along Another Vector  4. State and Prove Work Energy Theorem  5. Work Done and it's type 6. Kinetic energy 7. Work done by a variable force 8. work-energy theorem for a variable force 9. The concept of potential energy 10.  The conservation of mechanical energy 11. The potential energy of a spring 12. Power 13. Collisions 14. Collisions-One-Dimension-1D-Collision   15. Collisions-two-Dimension-2D-Collision   16. NCERT Solution Class 11 Physics Chapter 5 Work, Energy and Power  

Collisions in Two Dimensions A two-dimensional collision occurs when two bodies collide and move in a plane after collision. Linear momentum is conserved in such collisions. Since momentum is a vector quantity, its conservation must be applied separately along the x-axis and y-axis. Consider Mass m₁ moving initially with velocity $ u$ . Mass m₂ initially at rest. After collision: m₁ moves with velocity v₁  at angle θ₁ . m₂ moves with velocity v₂  at angle θ₂ . Conservation of Linear Momentum Along the x-axis $$ m_1 u=m_1v_{1}\cos\theta_1+m_2v_{2}\cos\theta_2 $$ Along the y-axis $$ 0=m_1v_{1}\sin\theta_1-m_2v_{2}\sin\theta_2 $$ Unknown Quantities Usually, the known quantities are: $$ \{m_1,\;m_2,\;u\} $$ The unknown quantities are: $$ \{v_{1},\;v_{2},\;\theta_1,\;\theta_2\} $$ Thus, there are four unknowns but only two momentum equations. Special Case: One-Dimensional Collision If $$ \theta_1=\theta...

Collisions in One Dimension (1D Collision) Introduction A one-dimensional collision is a collision in which the motion of both bodies before and after collision takes place along the same straight line. Completely Inelastic Collision Elastic Collision 1. Completely Inelastic Collision In a completely inelastic collision, the colliding bodies stick together and move with a common velocity after collision. Given Mass m₁ moves with initial velocity u  and mass m₂ is initially at rest. \[ \theta_1=\theta_2=0 \] Conservation of Momentum \[ m_1 u=(m_1+m_2)v \] Therefore, \[ v=\frac{m_1}{m_1+m_2} u \] Final Velocity: \[ \boxed{v=\frac{m_1}{m_1+m_2} u} \] Loss of Kinetic Energy Initial kinetic energy: \[ K_i=\frac{1}{2}m_1 u^{2} \] Final kinetic energy: \[ K_f=\frac{1}{2}(m_1+m_2)v^{2} \] Loss in kinetic energy: \[ \Delta K = \frac{1}{2}m_1 u^{2} -\frac{1}{2}(m_1+m_2)v^{2} \] Substituting \[ v=\frac{m_1}{m_1+m_2} u \...

5.11 COLLISIONS Introduction In Physics, some quantities remain conserved during interactions between bodies. Two important conserved quantities are: Linear Momentum Energy Collisions provide practical applications of these conservation laws. Examples: Billiards, Carrom, Marbles, Cricket Ball striking a Bat. Collision A collision is a short-duration interaction between two bodies during which they exert large forces on each other, resulting in changes in their velocities. Collision of Two Particles Consider two particles: Mass $m_{1}$  moving with initial velocity $v_{1i}$ Mass $m_{2}$  initially at rest Before Collision $$u_1=v_{1i}$$ $$u_2=0$$ Particle m₁ moves along the positive x-axis towards particle m₂. After Collision m₁ moves with velocity v₁f making angle θ₁ with the x-axis. m₂ moves with velocity v₂f making angle θ₂ with the x-axis. The collision changes both speed and direction of motion. Conservation of Li...