JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II ELECTROMAGNETIC THEORY AND TRANSMISSION LINES Previous Question Paper (November/December - 2020 - R15)
Answer any Five Questions. All Questions Carry Equal Marks.
Main
Derive the expression of electric field intensity due to uniform line charge.
Answer
Consider an infinitely long line charge with uniform charge density ρL (C/m) placed along the z-axis. To find the electric field intensity E at a radial distance r from the line, we use Gauss's Law in integral form: ∮ D · dS = Qenclosed. Due to cylindrical symmetry, the electric flux density D has only a radial component Dr, and the field is independent of φ and z.
We choose a cylindrical Gaussian surface of radius r and length L centered on the z-axis. The surface consists of three parts: the top disk, the bottom disk, and the curved side surface. The flux through the top and bottom disks is zero because the electric field is directed radially outward, perpendicular to the surface normal vectors. The total flux is therefore only through the curved side surface:
The total charge enclosed by this surface is Q = ρLL. Applying Gauss's Law:
Since D = ε0E for free space, the electric field intensity is:
Given V= 5x3y2z and ε=2.25ε0, find i) E at point P (-3, 1, 2) ii) ρv at P.
Answer
Given V = 5x3y2z and ε = 2.25ε0.
i) The electric field E is the negative gradient of the potential V:
At point P(-3, 1, 2):
ii) To find the volume charge density ρv, use Poisson's equation ∇·D = ρv, where D = εE = 2.25ε0E:
At P(-3, 1, 2):
Explain any one application of Gauss’s Law.
Answer
Sign in to view the complete answer paper.
Define and explain the following: i) Electric flux density D ii) Electric field intensity E.
Answer
Sign in to view the complete answer paper.
Briefly discuss about magnetic scalar and vector potentials.
Answer
Sign in to view the complete answer paper.
Explain the applications of Ampere’s Circuit Law.
Answer
Sign in to view the complete answer paper.
The electric field in air is given by E=ρte-ρ-t aφ V/m. Find B and J.
Answer
Sign in to view the complete answer paper.
Show that another form of Faraday’s law is E = -∂A/∂t, where A is the magnetic vector potential.
Answer
Sign in to view the complete answer paper.
Show that in a good conductor, the skin depth δ is always much shorter than the wavelength.
Answer
Sign in to view the complete answer paper.
A copper wire is 0.1mm thick. Find the frequency at which the thickness of the trace is equal to the skin depth.
Answer
Sign in to view the complete answer paper.
State and prove Poynting theorem.
Answer
Sign in to view the complete answer paper.
Prove that a line of finite length terminated by its characteristic impedance Z0 is equal to a line of infinite length.
Answer
Sign in to view the complete answer paper.
Describe the losses in transmission lines.
Answer
Sign in to view the complete answer paper.
Describe the applications and characteristics of λ/2 and λ/4 lossless transmission line elements.
Answer
Sign in to view the complete answer paper.
What is stub? Why are short circuited stubs are preferred to open circuited ones? Explain.
Answer
Sign in to view the complete answer paper.