- Electromagnetic theory is a discipline concerned with the study of charges at rest and in motion.
- Electromagnetic principles are fundamental to the study of electrical engineering and physics.
- Electromagnetic theory is also indispensable to the understanding, analysis and design of various electrical, electromechanical and electronic systems.
- Applications:RF communication, Microwave Engineering, Antennas, Electrical Machines, Satellite Communication, Atomic and nuclear research, Radar Technology, Remote sensing, Quantum Electronics, VLSI, etc.
- Electromagnetic theory can be thought of as generalization of circuit theory.
- There are certain situations that can be handled exclusively in terms of field theory.
- In electromagnetic theory, the quantities involved can be categorized as source quantities and field quantities.
- Source of electromagnetic field is electric charges: either at rest or in motion.
- However an electromagnetic field may cause a redistribution of charges that in turn change the field and hence the separation of cause and effect is not always visible.
- Electric charge is a fundamental property of matter.
- Electromagnetic fields are caused by electric charges at rest and in motion.
- Positive and negative electric charges are sources of the electric fields and moving electric charges yielding a current is the source of magnetic fields.
- Charge exist only in positive or negative integral multiple of electronic charge, -e, e = 1.60 × 10-19 coulombs.
- Time-varying electric and magnetic fields are coupled in an electromagnetic field radiating from the source.
- Electromagnetic theory deals directly with the electric and magnetic field vectors where as circuit theory deals with the voltages and currents.
- Voltages and currents are integrated effects of electric and magnetic fields respectively.
- Magnetic flux density (B) with the unit T (Tesla or volt-second per square meter)
- Magnetic field intensity (H) with the unit A/m (Ampere per meter)
- Electric field intensity (E) with the unit V/m (Volt per meter)
- Electric flux density (D) with the unit C/m2 (Coulomb per square meter)
Electrostatics
Charge Distribution : In electrostatics we deal with point charges and different types of charge distriubutions like volume charge distribution, line charge distribution and surface charge distribution.Volume Charge Distribution :
- It is defined as charge per unit volume.
where, ΔQ is small amount of charge in small volume ΔV.
- The total charge within a defined volume is obtained by taking the volume integral throughout the volume.
Where, ρv = volume charge density, and dV = Differential volume
Line Charge Distribution:- In line charge distribution, whole the charge is linearly distributed along the length of the line and it is defined by liner charge density.
- It is the charge per unit length.
where, ρL = Linear charge density, and dL = Differential length
Surface (Sheet) Charge Distribution:- In surface charge distribution, the charge is uniformly distributed over the surface of sheet and it is defined by surface charge density.
- It is charge per unit surface area.
Here, ρS = Surface charge density, and dS = Differential area.
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