Topics
Electric Charges and Fields
- Electric Charge
- Conductors and Insulators
- Basic 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
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
Current Electricity
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
Magnetic Effects of Current and Magnetism
Electromagnetic Induction and Alternating Currents
Moving Charges and Magnetism
- Electromagnetism
- Magnetic force
- Motion in a Magnetic Field
- Magnetic Field Due to a Current Element, Biot-savart Law
- Magnetic Field on 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
Magnetism and Matter
Electromagnetic Waves
Optics
Electromagnetic Induction
Alternating Current
- AC Voltage Applied to a Resistor
- Representation of AC Current and Voltage by Rotating Vectors - Phasors
- AC Voltage Applied to an Inductor
- AC Voltage Applied to a Capacitor
- AC Voltage Applied to a Series LCR Circuit
- Phasor-diagram Solution
- Resonance
- Power in AC Circuit
- Transformers
- Overview: AC Circuits
Dual Nature of Radiation and Matter
Atoms and Nuclei
Electromagnetic Waves
- Concept of Electromagnetic Waves
- Displacement Current
- Sources of Electromagnetic Waves
- Nature of Electromagnetic Waves
- Electromagnetic Spectrum
- Overview of 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
- Optical Instruments
- Microscope and it’s types
- Telescope
- Overview of Ray Optics and Optical Instruments
Wave Optics
- Concept of 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
- Overview: Wave Optics
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
- Overview: Dual Nature of Radiation and Matter
The Special Theory of Relativity
Atoms
Nuclei
- Atomic Masses and Composition of Nucleus
- Size of the Nucleus
- Mass - Energy
- Nuclear Binding Energy
- Nuclear Force
- Radioactivity
- Forms of Energy > Nuclear Energy
- Nuclear Fission
- Nuclear Fusion
- Controlled Thermonuclear Fusion
- Overview: Nuclei
Semiconductor Electronics - Materials, Devices and Simple Circuits
- Concept of Semiconductor Electronics
- Classification of Metals, Conductors and Semiconductors
- Intrinsic Semiconductor
- Extrinsic Semiconductor
- n-type Semiconductor
- p-type Semiconductor
- Diode or p-n Junction
- Semiconductor Diode
- Application of Junction Diode as a Rectifier
- Overview: Semiconductor Electronics
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
Historical Background
For a long time, electricity and magnetism were treated as completely separate phenomena. In the early 19th century, experiments by Oersted and Ampere established that moving electric charges (currents) produce magnetic fields— for example, a compass needle deflects near a current-carrying wire. This raised a natural question:
Is the converse possible? Can a changing magnetic field produce an electric current?
The answer is an emphatic yes. The experiments of Michael Faraday (England) and Joseph Henry (USA), conducted around 1830, demonstrated conclusively that electric currents are induced in closed coils when they are subjected to time-varying magnetic fields. This phenomenon is called Electromagnetic Induction.
Faraday and Henry's discoveries are the foundation of every electric generator, transformer, and induction cooker in use today. Modern generators produce electrical power of up to 500 MW — enough to light 5 million 100-watt bulbs.
Experiment 1
Bar Magnet and Coil
Setup
- Coil C1 connected to a galvanometer G
- A bar magnet moved toward/away from the coil
Observations
| Action | Galvanometer Response |
|---|---|
| The North Pole pushed towards the coil | Deflects in one direction |
| Magnet held stationary | No deflection |
| The North Pole pulled away from the coil | Deflects in the opposite direction |
| The South Pole pushed towards the coil | Deflects in the direction opposite to that observed for the north pole approaching the coil |
| The Magnet moved faster | Produces a larger deflection |
| The coil moved towards a stationary magnet | Produces the same deflection as a moving magnet under equivalent conditions |
Conclusion
It is the relative motion between the magnet and the coil that is responsible for the induction of an electric current. Induction occurs only when the magnetic flux is changing.
Experiment 2
Current-Carrying Coil Replaces Magnet
Setup
- Coil C2 (connected to battery) replaces the bar magnet
- Coil C1 connected to galvanometer G
- C2 produces a steady magnetic field
Observations
| Action | Galvanometer Response |
|---|---|
| C2 moved towards C1 | Deflects in one direction |
| C2 moved away from C1 | Deflects in the opposite direction |
| Both coils stationary | No deflection |
| C1 moved while C2 stationary | Same effects observed |
Conclusion
Relative motion between two coils — one carrying current, the other connected to a galvanometer — induces current in the second coil. The agent of induction is once again changing the magnetic flux.
Experiment 3
Two Stationary Coils; Current Changed
Setup
- Both coils, C1 and C2, are held stationary
- C2 is connected to a battery through a tapping key K
- C1 is connected to the galvanometer G
Observations
| Action | Galvanometer Response |
|---|---|
| Key K pressed (current switched on) | Momentary deflection |
| Key held continuously pressed | No deflection |
| Key released (current switched off) | Momentary deflection in the opposite direction |
| An iron rod was inserted between the coils | Deflection dramatically increases |
Conclusion
Relative physical motion is NOT necessary for electromagnetic induction. A changing current in one coil changes its magnetic field, which changes the flux through the nearby stationary coil, thereby inducing an emf. Inserting an iron rod strengthens the magnetic field and amplifies the effect.
Example
Question: Consider Experiment 6.2.
- What would you do to obtain a large deflection of the galvanometer?
- How would you demonstrate the presence of an induced current in the absence of a galvanometer?
Solution:
(a) To obtain a large deflection, one or more of the following steps can be taken:
- Put a soft iron rod inside coil C₂ — it strengthens the magnetic field
- Connect C₂ to a more powerful battery — stronger current = stronger field
- Move the coils faster towards each other — faster motion = faster flux change = bigger EMF
(b) Simply replace the galvanometer with a small torch bulb.
When you move the coils relative to each other, the bulb will glow — proving that an induced current is flowing.
