# GTU Engineering Electromagnetic Question Paper Dec 2010

GUJARAT TECHNOLOGICAL UNIVERSITY

B.E. Sem-Vth Examination December 2010

Subject code: 151002

Subject Name: Engineering Electromagnetics

Total Marks: 70

Instructions:

1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.

Answer the following in brief                                                                                    08

(i)    ‘The divergence of the curl of a vector is zero’-Justify the statement with one example.

(ii)      Find the ay dot a^ and ax dot ae

(iii)   Given 60 p,C point charge located at the origin, find the total electric flux passing through that portion of the sphere r=26 cm bounded by 0<9<n/2 and 0<\$<n/2.

(iv)   For a coaxial cable find the electric field density inside the inner core, in between inner and outer core and outside the cable.

(i)      What is Gradient? with help of gradient prove that E= – V

(ii)     Find the volume charge density that is associated with D = pz2 sin2\$ ap + pz2 sin\$cos\$ a^ + p2z sin2\$ az c/m2

Q.2 (a) Derive the electric field intensity and electric field density due to an infinite and uniform line charge density.

(b) In the space, a line charge pL=80 nC/m lies along the entire Z-axis, while point charge of 100 nC each are located at (1,0,0) and (0,1,0). Find the potential difference VPq given P (2,1,0) and Q (3,2,5).

OR

(b) Given the flux density D = (2cos9/r3) ar + (sin9/r3) ae c/m2 evaluate both sides 0 < 9 < n/2 , 0< \$< of the divergence theorem for the region  defined by 1< r < 2 n/2.

Q.3 (a) Describe the boundary condition between free space and conductor. What is an  importance of boundary condition?

(b) Write Maxwell’s equations in point form and explain physical significance of  equations.

OR

Q.3 (a) Derive Poisson’s and Laplace’s equations and states their applications.

(b) Write Maxwell’s equations in integral form and explain their physical  significance.

Q.4 (a) State and explain Ampere’s circuital law. Find the magnetic field intensity due to long straight conductor using Ampere’s circuital law.

(b) A charge of 10 nC is moving with a velocity of 107(-0.5 ax + ay -0.71 az) m/s. Determine the force exerted on the test charge when

(i)     a magnetic induction B = ( ax + 2ay + 3 az) mWb/m2 is applied

(ii)   an electric field E = (3ax + 2ay + az) kV/m is applied.

(iii)             When B and E given above are applied simultaneously.

OR

Q.4 (a) What is curl? With help of curl meter explain the physical interpretation of curl and state its applications.

(b) A filamentary current of 10 A is directed in from infinity to the origin on the positive x axis, and then back to infinity along the positive y axis. Use the Biot- Savart law to find H at P (0,0,1)

Q.5 (a) Define and explain the following terms:

(i) Magnetization                        (ii) Polarization

(iii)   Skin effect and (iv) Standing wave ratio

(b) Write short note on:

(i)     Wave motion in free space

(ii)   Magnetic boundary condition

OR

Q.5 (a) Define and explain the following terms:

(i)     Poynting Vector (ii) The scalar and Vector magnetic potential

(iii) Hall  effect (iv) Retarded Potential

(b) (i) Transform the 5ax vector to spherical coordinate at A(x = 2,y = 3, z =1).

(ii)  Given V = (10/r2 ) sin9cos\$, Find the electric flux density at (2,n/2,0)