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| Latest Science NCERT Notes and Solutions (Class 12th) | ||||||||||||||
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Latest Class 12th Physics NCERT Concepts & Solutions
1. Electric Charges And Fields
This chapter introduces electrostatics, the study of stationary electric charges. It covers the concept of electric charge, its properties (quantisation, conservation), and methods of charging bodies. **Coulomb's Law** describes the force between point charges ($\textsf{F} = \frac{1}{4\pi\varepsilon_0} \frac{\textsf{q}_1\textsf{q}_2}{\textsf{r}^2}$). The chapter defines electric field ($\vec{\textsf{E}}$) and electric field lines. **Gauss's Law** ($\oint \vec{\textsf{E}} \cdot \textsf{d}\vec{\textsf{A}} = \frac{\textsf{q}_\text{enclosed}}{\varepsilon_0}$) and its applications for finding electric fields due to simple charge configurations (e.g., infinite wire, plane sheet) are discussed.
2. Electrostatic Potential And Capacitance
This chapter explores the concept of electrostatic potential ($\textsf{V}$), defined as potential energy per unit charge, and potential difference. The relationship between electric field and potential ($\textsf{E} = -\frac{\textsf{dV}}{\textsf{dr}}$) is explained. Equipotential surfaces and their properties are discussed. The concept of capacitance ($\textsf{C} = \frac{\textsf{Q}}{\textsf{V}}$), a measure of a conductor's ability to store charge, is introduced. Capacitors, their combinations (series and parallel), and the energy stored in a capacitor ($\textsf{U} = \frac{1}{2}\textsf{CV}^2$) are covered, along with the effect of dielectrics.
3. Current Electricity
This chapter deals with electric current, the flow of charge. It defines current ($\textsf{I} = \frac{\textsf{dQ}}{\textsf{dt}}$) and drift velocity. **Ohm's Law** ($\textsf{V = IR}$) is central, relating voltage, current, and resistance ($\textsf{R} = \rho\frac{\textsf{L}}{\textsf{A}}$). Concepts like resistivity, conductivity ($\sigma = \frac{1}{\rho}$), and their dependence on temperature are discussed. Series and parallel combinations of resistors, internal resistance of a cell, and **Kirchhoff's laws** are applied to analyze electric circuits. The chapter also covers the heating effect of current ($\textsf{H} = \textsf{I}^2\textsf{Rt}$) and electric power ($\textsf{P} = \textsf{VI}$).
4. Moving Charges And Magnetism
This chapter establishes the connection between electricity and magnetism, showing that moving charges produce magnetic fields. It introduces the **Biot-Savart Law** and **Ampere's Circuital Law** for calculating magnetic fields due to various current distributions (straight wire, circular loop, solenoid). The **Lorentz force** ($\vec{\textsf{F}} = \textsf{q}(\vec{\textsf{E}} + \vec{\textsf{v}} \times \vec{\textsf{B}})$) acting on a charge in electric and magnetic fields is explained. Magnetic force on a current-carrying conductor and torque on a current loop are discussed, leading to the principle of moving coil galvanometers.
5. Magnetism And Matter
This chapter explores the magnetic properties of materials. It introduces concepts like magnetic field lines, Earth's magnetism, and magnetic elements. Different magnetic materials – diamagnetic, paramagnetic, and ferromagnetic – are discussed, explaining their behaviour in external magnetic fields based on their microscopic properties and **Curie's Law**. The chapter also touches upon permanent magnets and electromagnets, explaining how specific materials are chosen for these applications based on their magnetic properties like retentivity and coercivity.
6. Electromagnetic Induction
This chapter introduces electromagnetic induction, the phenomenon where a changing magnetic flux through a coil induces an electromotive force (emf) and hence current. **Faraday's laws of induction** and **Lenz's Law** (stating that the induced current opposes the change causing it) are central. Concepts like motional emf (induced due to motion) and self and mutual inductance (measures of how a changing current in one coil induces emf in itself or a nearby coil) are explained. The working principle of AC generators is also covered.
7. Alternating Current
While previous chapters focused on Direct Current (DC), this chapter deals with Alternating Current (AC), which periodically reverses direction. It introduces AC voltage and current, phasors, and the analysis of AC circuits containing resistors (R), inductors (L), and capacitors (C), individually and in series (LCR circuit). Concepts like impedance, reactance, phase difference, resonance, and **power in AC circuits** are discussed. The working principle of transformers, essential for transmitting AC power over long distances, is also explained.
8. Electromagnetic Waves
This chapter introduces electromagnetic waves, disturbances that propagate through space carrying energy, and are composed of oscillating electric and magnetic fields perpendicular to each other and the direction of propagation. **Maxwell's equations** (though not derived in detail) are the basis. The chapter discusses the characteristics of electromagnetic waves (e.g., speed of light $c = \frac{1}{\sqrt{\mu_0\varepsilon_0}}$) and explores the entire electromagnetic spectrum, from radio waves to gamma rays, highlighting their diverse properties and applications in communication, medicine, and technology.
9. Ray Optics And Optical Instruments
This chapter treats light as rays propagating in straight lines, forming the basis of geometric optics. It covers reflection and refraction of light from surfaces, particularly spherical mirrors and lenses. **The mirror formula** ($\frac{1}{\textsf{v}} + \frac{1}{\textsf{u}} = \frac{1}{\textsf{f}}$) and **lens formula** ($\frac{1}{\textsf{v}} - \frac{1}{\textsf{u}} = \frac{1}{\textsf{f}}$) are used to locate images. Concepts like total internal reflection and dispersion of light through a prism are discussed. The chapter concludes with the working principles of optical instruments like the human eye, microscopes, and telescopes.
10. Wave Optics
Moving beyond ray optics, this chapter treats light as waves to explain phenomena that cannot be described by geometric optics. **Huygens' principle** is introduced to explain wave propagation. **Interference** (constructive and destructive superposition of waves, leading to patterns like in **Young's double-slit experiment**) and **diffraction** (bending of waves around obstacles) are explained. The chapter also introduces polarization, a property specific to transverse waves, and discusses its applications, providing a deeper understanding of light's nature.
11. Dual Nature Of Radiation And Matter
This chapter explores the revolutionary concept that light and matter exhibit both wave-like and particle-like properties. It discusses the **photoelectric effect**, explained by **Einstein's theory of photons** ($\textsf{E = h}\nu$), demonstrating the particle nature of light. **De Broglie's hypothesis** ($\lambda = \frac{\textsf{h}}{\textsf{p}}$) proposes the wave nature of matter particles, confirmed by experiments like electron diffraction. This dual nature is a cornerstone of quantum mechanics and significantly altered our understanding of the physical world.
12. Atoms
This chapter delves into the structure of the atom, moving from Rutherford's nuclear model to **Bohr's model** for the hydrogen atom. Bohr's postulates are used to explain the stability of atoms and the origin of spectral lines. Concepts like energy levels, ionisation energy, and emission/absorption spectra are discussed. The chapter provides a quantitative analysis of the hydrogen atom's structure and properties based on Bohr's theory, paving the way for more advanced quantum mechanical models.
13. Nuclei
This chapter focuses on the atomic nucleus, its composition (protons and neutrons), size, and mass. Concepts like **mass defect** and **binding energy** are introduced to explain nuclear stability. Radioactivity – the spontaneous disintegration of unstable nuclei via alpha ($\alpha$), beta ($\beta$), and gamma ($\gamma$) emissions – is discussed, along with decay laws and half-life. Nuclear energy through **fission** (splitting of heavy nuclei, used in reactors) and **fusion** (combining light nuclei, powering stars) are explained, highlighting their immense energy potential and applications.
14. Semiconductor Electronics: Materials, Devices And Simple Circuits
This chapter introduces semiconductors, materials with conductivity between conductors and insulators, crucial for modern electronics. It discusses intrinsic and extrinsic semiconductors (p-type and n-type) formed by doping. The formation and properties of a **p-n junction** are explained. Semiconductor devices like the **diode** (pn junction diode as a rectifier) and the **transistor** (as an amplifier and switch) are covered. Logic gates (AND, OR, NOT) and their representation are introduced, providing a basic understanding of digital electronics and their widespread use in devices.