GTU Electronics and Communication Engineering (Semester 5)
Engineering Electromagnetics
May 2015
Total marks: --
Total time: --
INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary


Do as directed.
1 (a) (i) What do you mean by electromagnetic wave? Where, when and why it is require? Explain in detail with help of Maxwell's equations.
4 M
1 (a) (ii) "The electric flux passing through any closed surface is equal to the total charge enclosed by that surface." Justify and prove.
4 M
Do as directed.
1 (b) (i) If V = 2 volts at x = 1mm and V = 0 volts at x = 0. Find E x at x = 1 mm in free space for the volume charge density -3×108ε0 x C/m3.
4 M
1 (b) (ii) Define with respect to the plane EM waves: (a) Phase, (b) Phase Constant and (c) Phase Velocity
3 M

2 (a) "Two charges exert on each other equal and opposite force." Justify and support your answer mathematically.
7 M
2 (b) Consider an electric field that is given by E = (4/ρ) aρ + 5az . (i) Find the unit vector aE in Cartesian components at (5, 10° ,1), (ii) Also find out the equation of the surface on which |E|= 6
7 M
2 (c) Calculate the total electric flux leaving the cubical surface formed by six planes x, y, z = +5 if the charge distribution is: (i) two point charges, 0.56 μC at (2.5, -3.6, - 4.7) and 1/7 μC at (-3, 4.5, -4.9); (ii) a uniform line charge of πμC/m at x = 3, y = 4.5; (iii) a uniform surface charge of 0.1 μC/m2 on the plane y = 4x.
7 M

3 (a) What do you mean by equipotential surface? Derive the expression of potential gradient.
7 M
3 (b) Verify Stoke's theorem for the field H = 6xy ax - 3y2 ay and the rectangular path around the region 2 ≤ x ≤5, -1≤ y ≤1 and z = 0. Let the positive direction of ds be az.
7 M
3 (c) Write the property of conductor and determine boundary conditions at a boundary between a conductor and free space or perfect dielectric.
7 M
3 (d) State and prove Uniqueness theorem.
7 M

4 (a) (i) Derive the expression for force on differential current element.
3 M
4 (a) (ii) A point charge Q = -50 nC is moving in a magnetic field of density
B=2 ax -3ay +5az mT with a velocity of 6×106 m/s. Calculate the force in the direction specified by the unit vector -0.48ax-0.6ay+0.64az.
4 M
4 (b) State Faraday's law and from Faraday's law derives the Maxwell's first equation in differential form and state the same.
7 M
4 (c) (i) A line charge ? L over a ring of radius "a" meter is lying in xy-plane at z =0. Find electric field intensity at any point on the z- axis.
4 M
4 (c) (ii) A uniform line charge of 10 nC/m is lying along z-axis. Find E and D at ρ =3m.
4 M
4 (d) What do you mean by dipole? Derive the approximate expression for Potential V and Electric field intensity E at a point in the free space.
7 M

5 (a) (i) Explain in detail: Skin Effect.
4 M
5 (a) (ii) The magnetic field intensity of a uniform plane wave in y -direction is 20 A/m, the wave is propagating in z-direction in free space and has frequency of 2 Grad/sec. Find wavelength, frequency, time period and amplitude of electric field
3 M
5 (b) What do you mean by perfect dielectric? Explain plane wave propagation in perfect dielectric and derive expression for velocity of propagation, intrinsic impedance, attenuation constant and phase constant for the same.
7 M
5 (c) 300 MHz EM wave is propagating in fresh water having μr=1 and ε0=78 has maximum amplitude of 0.1 V/m. Find phase shift constant, wavelength, velocity.
7 M
5 (d) What Poynting vector shows? Starting from Maxwell's curl equation find the expression for Poynting vector. Also discuss about each term of the expression.
7 M



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