AMIETE – ET (NEW SCHEME)   -  Code: AE63

 

Subject: ELECTROMAGNETICS & RADIATION SYSTEMS

Flowchart: Alternate Process: JUNE 2010Time: 3 Hours                                                                                                     Max. Marks: 100

 

 

NOTE: There are 9 Questions in all.

·      Question 1 is compulsory and carries 20 marks. Answer to Q.1 must be written in the space provided for it in the answer book supplied and nowhere else.

·      Out of the remaining EIGHT Questions, answer any FIVE Questions. Each question carries 16 marks.

·      Any required data not explicitly given, may be suitably assumed and stated.

 

 

Q.1       Choose the correct or the best alternative in the following:                                  (210)

       

             a.  The potential at any point due to point charge is given by ________.

 

                  (A)                                    (B)

                  (C)                                     (D)

 

             b. Ampere’s law in differential form is given by _________. 

 

                  (A)                                     (B)

                  (C)                                     (D)

 

             c.  The magnitude of electric field at the origin due to a point charges of             6.44   located at (4,2, ) is ________.

 

                  (A) 2V/m                                             (B) 1V/m

                  (C) 2.5V/m                                          (D) 3V/m

 

             d.  Laplace equation in Cartesian Coordinate is ____________.

 

                  (A)

                  (B)

                  (C)

                  (D)

             e.  Stokes’ Theorem states that ______________.

 

                  (A)                     (B)

                  (C)                      (D)

 

             f.   The intrinsic impedance of free space is ________________.

       

                  (A) 73                                               (B) 277

                  (C) 120                                             (D) 377

       

             g. If  the charge density at the point (1, 1, 2) m is _____________.

 

                  (A) 12 c/m3                                          (B) 50 c/m3

                  (C) 52 c/m3                                          (D) 85 c/m3

 

             h.  Which one of the following is a non resonant antenna?

 

(A)        The rhombic antenna.                 (B) The folded dipole.

                  (C)    The broadside array.                   (D) The end-fire array.

 

             i.   Top loading is sometimes used with an antenna in order to increase its ______.

 

                  (A) effective height                                (B) bandwidth

                  (C) beamwidth                                     (D) input capacitance

 

             j.   An ungrounded antenna near the ground ________.

 

                  (A) acts as a single antenna of twice the height

                  (B) is unlikely to need an earth mat

                  (C) acts as an antenna array

                  (D) must be horizontally polarized

 

 

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

 

 

  Q.2     a.   State and explain Gauss law and derive Maxwell’s equation using Gauss law.                                 (10)

 

             b.   Uniform line charge of 0.4 µC/m and are located in the x = 0 plane at   y = 0.6 and y = 0.6 m, respectively. Let ε= εo. Find E at: (i) P(x, 0, z);       (ii) Q (2, 3, 4).                                     (6)

 

  Q.3    a.                                                              Define potential and Electric field density at a point in an electric field and obtain the relation between them.                                                                (8)

 

           b.    A point charge of 12 nC is located at the origin. Four uniform line charges are located in the x = 0 plane as follows: 80nC/m at y = 1 and 5 m, 50 nC/m at y = 2 and 4m. (i) Find D at P(0, 3, 2). (ii) How much electric flux crosses the plane   y = 3, and in what direction? (iii) How much electric flux leaves the surface of a sphere, 4 m in radius, centered at  C(0, 3, 0)?                                (8)

                 

Q.4     a.      Explain the significance of normal and tangential components at the boundary regions and derive the relation for the same for perfect dielectric material.                                                          (8)                         

             b.   Given the current density J = :    (i) find the total current crossing the plane y = 1 in the ay direction in the region 0 < x, y < 1, 2 < z < 3 by: (ii) integrating J.dS over the surface of the cube; (iii) employing the divergence theorem.                           (8)

                                      

  Q.5     a.   State and prove Stokes’ theorem.                                                                      (8)

 

             b.   A current sheet K = 8ax A/m flows in the region m < y < 2 m in the plane      z = 0. Calculate H at P(0, 0, 3).                                                                                                                 (8)

 

  Q.6     a.   Explain magnetic boundary conditions and derive an expression for tangential components.             (8)

 

             b.   Explain the concept of magnetic circuits as applied to electromagnetic.                (8)

       

  Q.7     a.   Express Maxwell’s equation in both differential and integral form for a time varying field and explain it.                                                                   (8)

 

             b.   The Electric Field of a uniform plane wave is given by,                                        (8)

                                    

                   Find,                                                  

i)    frequency                                                                                                  

                         ii)   wavelength   

                        iii)   direction of propagation of the wave, and also                                            

                        iv)   the associated magnetic field                                                                  

                                                                                                                                                                                                                                                                                                Q.8      a.   Explain critical frequency and MUF for an ionospheric wave propagation and

                   find the relation between them.                                                                           (5)

 

             b.   Explain how ionosphere region is formed and which are the regions present during day and night time.                                                                    (6)

                                                                                                        

             c.   Explain space wave propagation.                                                                        (5)

 

  Q.9     a.   With neat diagram explain the working of Broadside and End-fire array.            (10)

 

             b.   With reference to an antenna define the following terms:                                      (4)

                   (i)   Antenna resistance                      (ii)  Antenna efficiency

                   (iii) Band width                                    (iv) Beam width

 

             c.   An antenna has a radiation resistance of 73 ohm and loss resistance of 5 ohm. If the directivity is 0.8 find the efficiency and power gain.                    (2)