Fundamentals of Electromagnetic Theory (NEC-508)
Section-Wise Important Questions & Study Notes
SECTION–A
(Attempt all questions | 2 × 10 = 20)
This section checks basic concepts, definitions, and formulas.
Write short, crisp answers (2–3 lines).
1. Unit Vector Parallel to a Given Vector
To find a unit vector parallel to a vector A, divide the vector by its magnitude.
Unit vector = A / |A|
2. Faraday’s Law
Faraday’s law states that an EMF is induced in a circuit whenever the magnetic flux linking the circuit changes with time.
3. Electric Dipole Moment
Electric dipole moment is the product of charge magnitude and the distance between two opposite charges, directed from negative to positive charge.
4. Dielectrics and Their Types
Dielectrics are insulating materials that store electrical energy.
Types include polar and non-polar dielectrics.
5. Coulomb’s Inverse Square Law
The force between two point charges is directly proportional to the product of charges and inversely proportional to the square of the distance between them.
The force acts along the line joining the charges.
6. Types of Magnets & Magnetic Flux Lines
Types: permanent, temporary, and electromagnets.
Magnetic flux lines form closed loops, never intersect, and show direction from north to south.
7. Loss Tangent & Loss Angle
Loss tangent is the ratio of dielectric loss to stored energy.
Loss angle is the angle between current and voltage in a dielectric.
8. Displacement Current
Displacement current is the current produced due to time-varying electric fields, even in the absence of charge flow.
9. Energy Stored in Magnetic Field
Energy stored in a magnetic field is given by
W = ½ LI² or expressed in terms of magnetic field intensity.
10. Transformer EMF Equation EMF equation of transformer: E = 4.44 f N Φm
SECTION–B
(Attempt any THREE | 10 × 3 = 30)
Conceptual + derivation-based questions.
1. Area Using Spherical Coordinates
You must know: Spherical coordinate system
Differential area element Limits of integration
Write steps clearly and refer to diagram.
2. Electrostatic Boundary Conditions
Explain boundary conditions at conductor–free space interface: Tangential electric field
Normal electric flux density Continuity conditions
Include derivation and neat diagram.
3. Biot–Savart Law & Force Between Conductors
State Biot–Savart law and derive expression for magnetic field.
Then derive force per unit length between two parallel current-carrying conductors.
4. Uniform Plane Wave Problem
Numerical based on: Attenuation constant (α)
Phase constant (β) Magnetic field intensity (H)
Write formulas first, then substitute values.
5. Maxwell’s Equations Write all four Maxwell’s equations:
Integral form Differential form
Also explain physical meaning briefly.
SECTION–C
(Attempt any TWO | 5 × 2 = 10)
Mathematical and theorem-based questions.
1. Stokes’ Theorem
State the theorem, explain its meaning, and prove it using vector calculus.
2. Gradient, Divergence & Curl
Explain: Physical meaning
Mathematical expressions Use in different coordinate systems (Cartesian, cylindrical, spherical)
3. Divergence Theorem
State and prove divergence theorem. Explain its importance in electromagnetic theory.
