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| Non-Rationalised Science NCERT Notes and Solutions (Class 12th) | ||||||||||||||
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Class 12th Physics NCERT Notes and Solutions (Non-Rationalised)
1. Electric Charges And Fields
This chapter introduces the fundamental concepts of **electrostatics**, the study of stationary electric charges. It defines electric charge, its properties like quantisation and conservation, and methods of charging. **Coulomb's Law** describing the force between point charges ($\textsf{F} = \textsf{k} \frac{\textsf{q}_1\textsf{q}_2}{\textsf{r}^2}$) is central. The concepts of electric field ($\vec{\textsf{E}}$) as the force per unit charge, electric field lines, and electric dipole are discussed. **Gauss's Law** ($\oint \vec{\textsf{E}} \cdot \textsf{d}\vec{\textsf{A}} = \frac{\textsf{q}_\text{enclosed}}{\varepsilon_0}$) is introduced as a powerful tool for calculating electric fields for symmetric charge distributions, like a charged sphere or infinite wire, highlighting the fundamental interactions between charges.
2. Electrostatic Potential And Capacitance
Building on the concept of electric field, this chapter introduces **electrostatic potential** ($\textsf{V}$), defined as the potential energy per unit charge. The relationship between electric field and potential ($\textsf{E} = -\frac{\textsf{dV}}{\textsf{dr}}$) is crucial. **Equipotential surfaces** and their properties are discussed. The concept of **capacitance** ($\textsf{C} = \frac{\textsf{Q}}{\textsf{V}}$), the ability of a conductor to store charge, is explained. **Capacitors**, devices storing electrical energy, their combinations (series and parallel), and the energy stored in a capacitor ($\textsf{U} = \frac{1}{2}\textsf{CV}^2 = \frac{\textsf{Q}^2}{2\textsf{C}}$) are covered, along with the effect of introducing a **dielectric** medium between capacitor plates.
3. Current Electricity
This chapter shifts focus to moving charges, i.e., **electric current**. It defines electric current ($\textsf{I} = \frac{\textsf{dQ}}{\textsf{dt}}$) and drift velocity. **Ohm's Law** ($\textsf{V = IR}$) is fundamental, relating potential difference ($\textsf{V}$) across a conductor to the current ($\textsf{I}$) flowing through it and its resistance ($\textsf{R} = \rho\frac{\textsf{L}}{\textsf{A}}$). Resistivity ($\rho$), conductivity ($\sigma = \frac{1}{\rho}$), and their temperature dependence are discussed. **Kirchhoff's laws** (junction rule and loop rule) are introduced for analyzing complex electric circuits. The **heating effect of current** ($\textsf{H} = \textsf{I}^2\textsf{Rt}$) and **electric power** ($\textsf{P} = \textsf{VI}$) are also explained, highlighting energy transfer in circuits.
4. Moving Charges And Magnetism
This chapter establishes the fundamental connection between electricity and magnetism: **moving electric charges produce magnetic fields**. It introduces the concept of magnetic field ($\vec{\textsf{B}}$). The force experienced by a moving charge in electric and magnetic fields, the **Lorentz force** ($\vec{\textsf{F}} = \textsf{q}(\vec{\textsf{E}} + \vec{\textsf{v}} \times \vec{\textsf{B}})$), is discussed. The magnetic force on a current-carrying conductor is explained. Methods to calculate magnetic fields due to current distributions are introduced using the **Biot-Savart Law** and **Ampere's Circuital Law** (for straight wires, loops, solenoids). The chapter covers the torque on a current loop in a magnetic field and the principle of the moving coil galvanometer.
5. Magnetism And Matter
This chapter delves into the magnetic properties of materials and Earth's magnetism. It introduces key concepts like magnetic field lines, magnetic dipole moment, and the magnetic field of a bar magnet. Earth's magnetism is discussed, including magnetic elements (declination, dip, horizontal component). Different categories of magnetic materials – **diamagnetic**, **paramagnetic**, and **ferromagnetic** – are explained based on their behavior in external magnetic fields, relating their properties to microscopic magnetic moments. The chapter also introduces permanent magnets and electromagnets and the factors affecting their strength.
6. Electromagnetic Induction
This chapter introduces **electromagnetic induction**, the crucial phenomenon where a changing magnetic field or magnetic flux through a coil induces an electromotive force (emf) and hence an electric current. **Faraday's laws of induction** quantify the induced emf, while **Lenz's Law** provides its direction, stating that the induced current opposes the change causing it. Concepts like motional emf (induced due to conductor movement in a magnetic field) and **self and mutual inductance** (measures of how a changing current in one circuit induces emf in itself or a neighboring circuit) are explained. The working principle of the **AC generator** is also covered, demonstrating the conversion of mechanical energy into electrical energy.
7. Alternating Current
This chapter focuses on **alternating current (AC)** and voltage, which vary sinusoidally with time, as commonly supplied for domestic and industrial use. It introduces concepts like peak and RMS values of AC quantities. Analysis of simple AC circuits containing resistors (R), inductors (L), and capacitors (C), individually and in series (LCR circuits), is done using phasor diagrams and impedance. Concepts like reactance, impedance, phase difference between voltage and current, **resonance** (in LCR circuits), and **power in AC circuits** are discussed. The working principle of the **transformer**, vital for voltage transformation, is also explained.
8. Electromagnetic Waves
This chapter introduces **electromagnetic waves**, disturbances that propagate through space at the speed of light, carrying energy and momentum. They are composed of oscillating electric and magnetic fields perpendicular to each other and the direction of propagation. The chapter discusses their characteristics, including the relationship between the speeds of light, electric, and magnetic fields ($\textsf{c} = \frac{1}{\sqrt{\mu_0\varepsilon_0}}$). The **electromagnetic spectrum**, encompassing radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays, is presented, highlighting their properties and diverse applications in technology, communication, and medicine, illustrating the unifying nature of light and electromagnetism.
9. Ray Optics And Optical Instruments
This chapter deals with **ray optics** or geometric optics, treating light as rays traveling in straight lines. It covers **reflection** of light from plane and spherical mirrors and **refraction** of light as it passes from one medium to another, introducing the laws of reflection and **Snell's Law** ($\textsf{n}_1 \sin \theta_1 = \textsf{n}_2 \sin \theta_2$). Image formation by mirrors and lenses (convex and concave) is analyzed using ray diagrams and the mirror/lens formulae ($\frac{1}{\textsf{v}} + \frac{1}{\textsf{u}} = \frac{1}{\textsf{f}}$ for mirrors, $\frac{1}{\textsf{v}} - \frac{1}{\textsf{u}} = \frac{1}{\textsf{f}}$ for lenses). **Total internal reflection** and its applications are discussed. The chapter explains the working of optical instruments like the human eye, simple and compound microscopes, and telescopes.
10. Wave Optics
Moving beyond the ray model, this chapter treats light as **waves** to explain phenomena like interference and diffraction. **Huygens' Principle** is introduced to describe wave propagation. **Interference**, the superposition of waves resulting in reinforcement or cancellation, is explained, with **Young's double-slit experiment** as a key demonstration (fringe width $\beta = \frac{\lambda\textsf{D}}{\textsf{d}}$). **Diffraction**, the bending of waves around obstacles or through apertures, is discussed (e.g., diffraction at a single slit). The chapter also introduces **polarization**, a property of transverse waves, and its applications, providing a deeper understanding of the wave nature of light.
11. Dual Nature Of Radiation And Matter
This revolutionary chapter explores the concept of **wave-particle duality**, stating that light and matter exhibit both wave-like and particle-like properties. It discusses the **photoelectric effect**, explained by **Einstein's photon theory** ($\textsf{E = h}\nu$, $\textsf{KE}_\text{max} = \textsf{h}\nu - \phi$), demonstrating the particle nature of light (photons). **De Broglie's hypothesis** ($\lambda = \frac{\textsf{h}}{\textsf{p}}$) proposes that matter particles (like electrons) also have wave properties, confirmed by experiments like electron diffraction. This dual nature is a cornerstone of quantum mechanics, fundamentally changing our view of the microscopic world.
12. Atoms
This chapter delves into the structure of the atom, focusing primarily on the **Bohr model** for the hydrogen atom. It discusses the experimental observations leading to atomic models, starting from Rutherford's nuclear model. **Bohr's postulates** regarding quantized energy levels and angular momentum are explained. The chapter uses Bohr's model to derive the energy levels, radii, and velocities of electrons in hydrogen-like atoms. It explains the origin of atomic spectra, particularly the hydrogen spectrum series (Lyman, Balmer, Paschen, Brackett, Pfund), based on electron transitions between energy levels. Limitations of Bohr's model are also mentioned.
13. Nuclei
This chapter focuses on the **atomic nucleus**, its composition (protons and neutrons), size, density, and mass. Concepts like **mass defect** ($\Delta \textsf{m}$) and **binding energy** ($\textsf{E}_\text{b} = \Delta \textsf{mc}^2$), which relate to nuclear stability, are introduced. **Radioactivity** – the spontaneous disintegration of unstable nuclei – is discussed, covering $\alpha$, $\beta$, and $\gamma$ decay, their properties, and decay laws ($N = N_0 e^{-\lambda t}$, half-life $T_{1/2} = \frac{0.693}{\lambda}$). **Nuclear energy** released during **fission** (splitting of heavy nuclei) and **fusion** (combining light nuclei, powering stars) is explained, highlighting their applications in power generation and weapons.
14. Semiconductor Electronics: Materials, Devices And Simple Circuits
This chapter introduces **semiconductors**, materials with conductivity between conductors and insulators, which form the basis of modern electronic devices. It discusses intrinsic and extrinsic semiconductors (**p-type** and **n-type**), created by doping with impurities. The formation and properties of a **p-n junction** are explained, including forward and reverse biasing and the depletion region. Semiconductor devices like the **p-n junction diode** (used as a rectifier to convert AC to DC) and the **transistor** (as an amplifier or switch) are covered. The chapter also introduces **logic gates** (AND, OR, NOT, NAND, NOR) as basic building blocks of digital circuits, demonstrating their truth tables and symbols.