12th class physics: electrostatics

• Class 12 physics covers a wide range of topics, including electrostatics, current electricity, magnetic effects of current and magnetism, electromagnetic induction and alternating currents, electromagnetic waves, optics, dual nature of radiation and matter, atoms, nuclei, semiconductor electronics, and communication systems.

Electrostatics

• Electric charges and fields are fundamental concepts.
• Electric charge is quantized, conserved, and additive.
• Coulomb’s law describes the force between two point charges.
• Electric field is the force per unit charge.
• Electric field lines provide a visual representation of electric fields.
• Electric dipole consists of two equal and opposite charges separated by a small distance.
• Electric dipole moment is a measure of the strength and direction of an electric dipole.
• Gauss’s law relates the electric flux through a closed surface to the enclosed charge.
• Applications of Gauss’s law include finding the electric field due to uniformly charged wires, planes, and spheres.
• Electric potential is the work done per unit charge to bring a charge from infinity to a point in an electric field.
• Potential difference is the difference in electric potential between two points.
• Equipotential surfaces are surfaces with constant electric potential.
• Capacitance is the ability of a conductor to store electric charge.
• Capacitors are devices used to store electrical energy.
• Parallel plate capacitor consists of two parallel conducting plates separated by a dielectric.
• Combination of capacitors can be in series or parallel.
• Energy stored in a capacitor is proportional to the square of the voltage.
• Dielectrics are insulating materials that increase the capacitance of a capacitor.
• Polarization of dielectrics occurs when the molecules align in an electric field.

Current Electricity

• Electric current is the rate of flow of electric charge.
• Ohm’s law relates voltage, current, and resistance.
• Resistance is the opposition to the flow of current.
• Resistivity is a property of the material that determines its resistance.
• Drift velocity is the average velocity of charge carriers in an electric field.
• Mobility is the drift velocity per unit electric field.
• Temperature dependence of resistance: resistance changes with temperature.
• Electrical energy and power: power is the rate at which electrical energy is consumed.
• Cells, emf, internal resistance: cells provide a source of constant voltage.
• Kirchhoff’s laws are used to analyze complex circuits.
• Wheatstone bridge is used to measure unknown resistances.
• Potentiometer is used to measure potential difference accurately.

Magnetic Effects of Current and Magnetism

• Magnetic field is produced by moving charges.
• Biot-Savart law describes the magnetic field due to a small current element.
• Ampere’s law relates the magnetic field around a closed loop to the current passing through the loop.
• Magnetic field due to a straight wire, circular loop, and solenoid.
• Force on a moving charge in a magnetic field.
• Force on a current-carrying conductor in a magnetic field.
• Torque on a current loop in a magnetic field.
• Moving coil galvanometer is used to measure small currents.
• Conversion of galvanometer into ammeter and voltmeter.
• Magnetic dipole and dipole moment.
• Magnetic field intensity due to a magnetic dipole.
• Earth’s magnetic field and magnetic elements.
• Magnetic properties of materials: diamagnetic, paramagnetic, and ferromagnetic substances.
• Hysteresis loop for ferromagnetic materials.
• Permanent magnets and electromagnets.

Electromagnetic Induction and Alternating Currents

• Electromagnetic induction is the production of emf due to changing magnetic flux.
• Faraday’s law of electromagnetic induction.
• Lenz’s law gives the direction of the induced emf.
• Motional emf is induced in a conductor moving in a magnetic field.
• Eddy currents are induced in conductors when subjected to changing magnetic fields.
• Self-induction is the induction of emf in a coil due to its own changing current.
• Mutual induction is the induction of emf in one coil due to changing current in another coil.
• Alternating current (AC) varies sinusoidally with time.
• AC voltage and current, RMS value, peak value, and average value.
• Reactance and impedance in AC circuits.
• LCR series circuit: resonance, power in AC circuits, power factor.
• Transformers are used to step up or step down AC voltage.

Electromagnetic Waves

• Electromagnetic waves are produced by oscillating charges.
• Displacement current is due to changing electric fields.
• Electromagnetic spectrum includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.
• Properties of electromagnetic waves, including speed, frequency, and wavelength.

Optics

• Reflection of light: laws of reflection, mirrors.
• Refraction of light: laws of refraction, refractive index.
• Total internal reflection and its applications.
• Lenses: lens maker’s formula, thin lens formula.
• Combination of lenses.
• Optical instruments: microscope, telescope.
• Wave optics: Huygens’ principle, wave nature of light.
• Interference of light: Young’s double slit experiment.
• Diffraction of light: diffraction due to a single slit.
• Polarization of light: methods of polarization.

Dual Nature of Radiation and Matter

• Photoelectric effect is the emission of electrons from a metal surface when light is incident on it.
• Einstein’s photoelectric equation.
• Particle nature of light: photons, energy and momentum of photons.
• Wave nature of matter: de Broglie hypothesis.
• de Broglie wavelength.
• Davisson-Germer experiment.

Atoms

• Atomic structure: Rutherford’s model, Bohr’s model.
• Energy levels, hydrogen spectrum.

Nuclei

• Nuclear structure: composition and size of nucleus.
• Mass-energy relation, nuclear binding energy.
• Nuclear fission and nuclear fusion.
• Radioactivity: alpha, beta, and gamma decay.
• Nuclear reactions.

Semiconductor Electronics

• Semiconductors: energy bands in solids, intrinsic and extrinsic semiconductors.
• p-n junction: depletion region, barrier potential.
• Semiconductor diode: forward and reverse bias.
• Rectifier: half-wave and full-wave rectifiers.
• Special purpose diodes: LED, photodiode, solar cell.
• Transistors: characteristics and applications.

Communication Systems

• Elements of a communication system.
• Modulation and demodulation.
• Types of modulation: amplitude modulation (AM), frequency modulation (FM), and phase modulation (PM).
• Bandwidth of signals and transmission medium.
• Propagation of electromagnetic waves in the atmosphere.