Topics
Electric Charges and Fields
- Electric Charges
- Conductors and Insulators
- Properties of Electric Charge
- Coulomb’s Law
- Forces between Multiple Charges
- Electric Field
- Electric Field Due to a System of Charges
- Physical Significance of Electric Field
- Electric Field Lines
- Electric Flux
- Electric Dipole
- Dipole in a Uniform External Field
- Continuous Charge Distribution
- Gauss’s Law
- Application of Gauss' Law
Electrostatics
Current Electricity
Electrostatic Potential and Capacitance
- Electric Potential and Potential Energy
- Electrostatic Potential
- Electric Potential Due to a Point Charge
- Potential Due to an Electric Dipole
- Potential due to a System of Charges
- Equipotential Surfaces
- Relation Between Electric Field and Electrostatic Potential
- Potential Energy of a System of Charges
- Potential Energy of a Single Charge
- Potential Energy of a System of Two Charges in an External Field
- Potential Energy of a Dipole in an External Field
- Electrostatics of Conductors
- Dielectrics and Polarisation
- Capacitors and Capacitance
- The Parallel Plate Capacitor
- Effect of Dielectric on Capacitance
- Combination of Capacitors
- Energy Stored in a Charged Capacitor
Magnetic Effects of Current and Magnetism
Current Electricity
- Electric Current
- Electric Currents in Conductors
- Ohm's Law
- Drift of Electrons and the Origin of Resistivity
- Mobility of Electrons
- Limitations of Ohm’s Law
- Resistivity of Various Materials
- Temperature Dependence of Resistivity
- Electrical Energy and Power in Conductors
- Cells, EMF, and Internal Resistance
- Cells in Series and in Parallel
- Kirchhoff’s Laws
- Wheatstone Bridge
Moving Charges and Magnetism
- Electromagnetism
- Magnetic force
- Motion in a Magnetic Field
- Magnetic Field Due to a Current-carrying Conductor: Biot-savart's Law
- Applications of Biot-Savart's Law > Magnetic Field at the Axis of a Circular Current-carrying Loop
- Ampere’s Circuital Law
- Solenoid
- Force Between Two Parallel Currents (Ampere’s Law)
- Torque on a Rectangular Current Loop in a Uniform Magnetic Field
- Circular Current Loop as a Magnetic Dipole
- Moving Coil Galvanometer
- Kirchhoff’s Laws
Electromagnetic Induction and Alternating Currents
Electromagnetic Waves
Magnetism and Matter
Optics
Electromagnetic Induction
Alternating Current
Dual Nature of Radiation and Matter
Atoms and Nuclei
Electromagnetic Waves
Electronic Devices
Ray Optics and Optical Instruments
- Ray Optics Or Geometrical Optics
- Reflection of Light by Spherical Mirrors
- Sign Convention for Reflection by Spherical Mirrors
- Focal Length of Spherical Mirrors
- Mirror Equation of Spherical Mirrors
- Refraction of Light
- Total Internal Reflection
- Applications of Total Internal Reflection
- Refraction at a Spherical Surfaces
- Refraction by a Lens
- Power of a Lens
- Combined Focal Length of Two Thin Lenses in Contact
- Refraction of Light through a Prism
- Introduction to Optical Instruments
- Microscope and it’s types
- Telescope
Wave Optics
- Introduction to Wave Optics
- Huygens Principle
- Refraction of a Plane Wave
- Refraction at a Rarer Medium
- Reflection of a Plane Wave by a Plane Surface
- Coherent and Incoherent Addition of Waves
- Interference of Light Waves and Young’s Experiment
- Diffraction of Light
- The Single Slit
- Seeing the Single Slit Diffraction Pattern
- Polarisation of Light
Communication Systems
Dual Nature of Radiation and Matter
- Understanding Dual Nature of Radiation and Matter
- Electron Emission
- Photoelectric Effect - Hertz’s Observations
- Photoelectric Effect - Hallwachs’ and Lenard’s Observations
- Experimental Study of Photoelectric Effect
- Effects of Intensity and Frequency on Photocurrent
- Photoelectric Effect and Wave Theory of Light
- Einstein’s Photoelectric Equation: Energy Quantum of Radiation
- Particle Nature of Light: The Photon
- Wave Nature of Matter
The Special Theory of Relativity
Atoms
Nuclei
Semiconductor Electronics - Materials, Devices and Simple Circuits
Communication Systems
- Detection of Amplitude Modulated Wave
- Production of Amplitude Modulated Wave
- Basic Terminology Used in Electronic Communication Systems
- Sinusoidal Waves
- Modulation and Its Necessity
- Amplitude Modulation (AM)
- Need for Modulation and Demodulation
- Satellite Communication
- Propagation of EM Waves
- Bandwidth of Transmission Medium
- Bandwidth of Signals
The Special Theory of Relativity
- The Special Theory of Relativity
- The Principle of Relativity
- Maxwell'S Laws
- Kinematical Consequences
- Dynamics at Large Velocity
- Energy and Momentum
- The Ultimate Speed
- Twin Paradox
Estimated time: 6 minutes
CBSE: Class 12
Formation of Electromagnetic Waves
- Stationary charges do not produce electromagnetic waves
- Charges in uniform motion (constant velocity) — do not produce electromagnetic waves
- Accelerating charges do produce electromagnetic waves
CBSE: Class 12
Mechanism of Wave Production
- An oscillating charge produces an oscillating electric field in the surrounding space
- This oscillating electric field generates an oscillating magnetic field
- The oscillating magnetic field, in turn, regenerates the oscillating electric field
- This process sustains itself — the fields keep regenerating each other as the wave propagates outward
CBSE: Class 12
Key Properties
- The frequency of the electromagnetic wave = frequency of oscillation of the charge
- The energy of the wave comes from the energy of the oscillating charge (the source)
CBSE: Class 12
Practical Limitation
- For visible light (e.g., yellow light ≈ 6 × 1014 Hz), an oscillating charge at that frequency would be needed
- Modern electronic circuits can oscillate only up to about 1011 Hz
- Therefore, it is not practical to generate visible light by setting up oscillating circuits
- Early demonstrations of EM wave production were hence done in the radio-wave region
CBSE: Class 12
History/Origin
| Scientist | Contribution |
|---|---|
| Heinrich Rudolf Hertz | First produced, broadcast, and received radio waves; confirmed Maxwell's theory; discovered the photoelectric effect |
| Jagdish Chandra Bose | Produced EM waves of shorter wavelengths (25 mm to 5 mm) in laboratory experiments in Calcutta |
| Guglielmo Marconi | Transmitted EM waves over many kilometres; initiated EM-wave-based communication |
CBSE: Class 12
Key Points: Sources of Electromagnetic Waves
- Only accelerating charges radiate electromagnetic waves
- An oscillating charge is a practical example of an accelerating charge
- The wave frequency equals the oscillation frequency of the source charge
- Energy of the wave is supplied by the source (oscillating charge)
- Modern circuits max out at ~1011 Hz — far below visible light frequencies (~6 × 1014 Hz)
- Early EM wave experiments were conducted in the radio-wave region due to this limitation
- Hertz → radio waves; Bose → short wavelength waves; Marconi → long-distance EM communication
