Topics
Electrostatics
Electric Charges and Fields
- Electric Charge
- 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
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
Electromagnetic Induction and Alternating Currents
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 Waves
Magnetism and Matter
Electromagnetic Induction
Optics
Alternating Current
Dual Nature of Radiation and Matter
Atoms and Nuclei
Electromagnetic Waves
- Introduction to Electromagnetic Waves
- Displacement Current
- Sources of Electromagnetic Waves
- Nature of Electromagnetic Waves
- Electromagnetic Spectrum
- Definition and Characteristics 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 Through a Prism
- Introduction to Optical Instruments
- Microscope and it’s types
- Telescope
Communication Systems
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
The Special Theory of Relativity
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
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
Introduction
Imagine holding a wire loop near a bar magnet. The more magnetic field lines that pierce through the loop, the stronger the effect on any current induced in it.
The physical quantity that measures this piercing of magnetic field through a surface is called magnetic flux.
Definition: Magnetic Flux
Magnetic flux linked with any surface is equal to the total number of magnetic lines of force passing normally through it.
Magnetic flux (ΦB) is the measure of magnetic field lines passing through a surface.
Formula: Magnetic Flux Through a Flat Surface
For a uniform magnetic field and a plane surface,
Where:
| Symbol | Meaning |
|---|---|
| ΦB | Magnetic flux |
| \[\vec B\] | Magnetic field |
| \[\vec A\] | Area vector of the surface |
| A | Area of the surface |
| θ | Angle between \[\vec B\] and \[\vec A\] |
Formula: Magnetic Flux Through a Non-uniform Field or Curved Surface
For a non-uniform magnetic field or a curved surface, divide the surface into very small area elements \[d\vec A\].
\[{\Phi_B=\int\vec{B}\cdot d\vec{A}}\]
Formula: Magnetic Flux Through a Coil
For a coil of N turns, when every turn contributes equally,
\[{\Phi=NBA\cos\theta}\]
This is the magnetic flux linkage of the coil.
Unit and Nature of Magnetic Flux
| Property | Magnetic Flux |
|---|---|
| Symbol | ΦB |
| SI unit | weber (Wb) |
| Equivalent unit | 1 Wb = 1 T⋅m2 |
| Also equivalent to | 1 Wb = 1 V⋅s |
| Nature | Scalar quantity |
| Dimensional formula | [ML2T−2A−1] |
Maximum, Zero and Negative Flux
| Orientation of magnetic field | Value of flux |
|---|---|
| Magnetic field parallel to the area vector | Maximum positive flux: ΦB = BA |
| Magnetic field at an angle θ to the area vector | ΦB = BA cos θ |
| Magnetic field perpendicular to the area vector | Zero flux: ΦB = 0 |
| Magnetic field opposite to the area vector | Negative flux: ΦB = −BA |
Key point: Flux is maximum when the magnetic field is perpendicular to the plane of the surface. Flux is zero when the magnetic field is parallel to the plane of the surface.
Factors Affecting Magnetic Flux
Magnetic flux increases when:
- Magnetic field B increases: A stronger magnetic field means more field lines per unit area.
- Area A increases: A larger surface allows more field lines to pass through it.
- Orientation changes: Flux depends on cos θ.
Magnetic Flux and Electromagnetic Induction
A change in magnetic flux is associated with electromagnetic induction.
Net Flux Through a Closed Surface
For a closed surface, the net magnetic flux is always zero.
- \[{\oint\vec{B}\cdot d\vec{A}=0}\]
This is Gauss's Law for Magnetism.
Magnetic field lines form closed loops; therefore, the number of field lines entering a closed surface equals the number leaving it.
Example 1
A rectangular loop of area 0.020 m2 is placed perpendicular to a uniform magnetic field of 5 T. Find the magnetic flux.
- ΦB = BA cos θ
- ΦB = (5)(0.020) cos 0°
- ΦB = 0.10 Wb
Example 2
A circular loop of area 0.020 m2 is placed in a magnetic field of 1 T. The magnetic field makes an angle of 60° with the normal to the loop. Find the magnetic flux.
- ΦB = BA cos θ
- ΦB = (1)(0.020) cos 60°
- ΦB = 0.010 Wb
