ElectroMagnetic Theory Concepts & Solved Numericals

1. Define A Uniform Plane Wave. Answer: In an uniform plane wave the electric and magnetic field vectors both lie in a plane and all such planes are parallel to each other. Also the amplitude and phase of vectors E and H are constant over the planes & they are always normal to the direction pf propagation. 2. State Gauss Divergence Theorem. Answer: This theorem states that the net flux of a vector field F over any closed surface S is equal to the volume integral of the divergence of that vector field over the volume enclosed by the surface S . Mathematically it is expressed as: 3. State Stoke’s Theorem. Answer: This theorem states that the line integral of vector field A around the closed curve forming the periphery of any surface S is equal to surface integral of the curl of that vector field taken over surface S bound by the curve forming periphery of the surface. Mathematically it is expressed as: 4. What Do You Understand By Displacement Current

01. State Three Ways In Which Forces Due To Magnetic Fields Can Be Experienced? Answer: There are at least three ways in which force due to magnetic fields can be experienced. The force can be due to a moving charged particle in a magnetic field. on a current element in an external magnetic field. between two current elements. 02. State The Lorentz Force Equation? Answer: The Lorentz force equation relates the force acting on a particle with charge Q in the presence of EM fields. It expresses the fundamental law relating EM to mechanics. F = Q(E + u * B) = m ( du/dt) Based on the Lorentz force law, the force experienced by a current element Idl in a magnetic field B is dF = I dl * B From this, the magnetic field B is defined as the force per unit current element. 03. Define Magnetic Torque? Answer: The torque T (or mechanical moment of force) on the loop is the vector product of the force F and iho moment arm r. T = r X F and magnetic torque is meas

01. How Can Materials Be Classified In Terms Of Their Electrical Properties? Answer:  Materials can be classified roughly as conductors (σ >> 1, ε r = 1) and dielectrics ( σ << 1, ε r  ≥ 1 ) in terms of their electrical properties  σ  and  ε r  where  σ  is the conductivity and  ε r  is the dielectric constant or relative permittivity. A material with high conductivity ( σ >> 1) is referred to as a metal whereas one with low conductivity ( σ << 1 ) is referred to as an insulator. A material whose conductivity lies somewhere between those of metals and insulators is called a semiconductor. 02. Define Superconductor? Answer: The conductivity of metals generally increases with decrease in temperature. At temperatures near absolute zero (T = 0°K), some conductors exhibit infinite conductivity and are called superconductors. Lead and aluminum are typical examples of such metals. 03. Why Conductor Is Called An Equipotential Body? What Are Perfect Con

1. What Do You Mean By Dielectric Constant Of A Material ? Answer: Dielectric constant (k) or relative permittivity (ε r ) is defined as the ratio of capacitance of a capacitor with dielectric to the capacitance of same capacitor without dielectric. It generally describes the ability of a material to polarize and store a charge. Mathematically, k or ε r = C/C 0 . [Since C = q/V, we have ε r = E 0 /E = V 0 /V = ε/ε r ]. 2. Define Dielectric Medium. Answer: Dielectric is a material in which energy can be stored by the polarization of the molecules. It is a material that increases the capacitance or charge storage ability of a capacitor. Ideally, a dielectric is an insulator and does not contain free charge. However, in the presence of external field it exhibits a relative displacement of opposite bound charges and hence the polarization of the medium. Due to polarization induced surface charges tend to weaken the original field within the dielectric. [The resultan

1. State Stokes Theorem. Answer: The line integral of a vector around a closed path is equal to the surface integral of the normal component of its curl over any surface bounded by the path ∫ H.dl = ∫ ∫ ( ∆ x H ) ds where, H is the Magnetic field intensity 2. State The Condition For The Vector F To Be Solenoidal. Answer: ∆ . F = 0 where, F = A i + B i + C i 3. State The Condition For The Vector F To Be Irrotational. Answer: ∆ x F = 0 where, F = A i + B i + C i 4. Give The Relationship Between Potential Gradient and Electric Field. Answer:  E = - ∆V where, E represents Electric Field Intensity and V represents Electric Potential 5. What Is The Physical Significance Of div D ? Answer: The divergence of a vector flux density is electric flux per unit volume leaving a small volume. This is equal to the volume charge density. 6. What Are The Sources Of Electric Field & Magnetic Field? Answer: Stationary charges produce electric field that are

The differences between Conduction Current and displacement current are: 1. Conduction current obeys ohm's law as V = (I / R) but displacement current does not obey ohm's law. 2. Conduction current density is represented by  whereas displacement current density is given by 3. Conduction current is the actual current whereas displacement current is the apparent current produced by time varying electric field.

1) An electric field strength of 10 µV/m is to be measured at an observation point θ = π/2, 500 km from a λ/4 monopole antenna operating in air at 50 MHz. (a) What is the length of the dipole? (b) Calculate the current that must be fed to the antenna. (c) Find the average power radiated by the antenna. (d) If a transmission line with Z o  = 75 Ω is connected to the antenna, determine the standing wave ratio. --- For Solution    CLICK HERE . 2) Calculate the directivity of The Hertzian Monopole. The quarter-wave Monopole.   ---  For Solution    CLICK HERE . 3) A certain antenna with an efficiency of 95% has maximum radiation intensity of 0.5 W/sr. Calculate its directivity when (a) The input power is 0.4 W (b) The radiated power is 0.3 W      ---  For Solution    CLICK HERE . 4) Evaluate the directivity of an antenna with normalized radiation intensity    ---  For Solution    CLICK HERE . 5) Determine the maximum effective area of a Hertzian dipole of length 1