Deemed University 2011 B.Tech Electrical and Electronics Engineering University: Lingayas University Term: V Title of the : Engineering Electro-magnetics - Question Paper

Roll No. ..

 

Lingayas University

B.Tech. 2^nd Year (Term V)

Examination Feb 2011

Engineering Electro-magnetics (EE - 204)

 

[Time: 3 Hours] [Max. Marks: 100]

 

Before answering the question, candidate should ensure that they have been supplied the correct and complete question paper. No complaint in this regard, will be entertained after examination.

 

Note: Attempt five questions in all. All questions carry equal marks. Question no. 1 is compulsory. Select two questions from Section B and two questions from Section C.

Section A

Q-1. Part A

Select the correct answer of the following multiple choice questions. [10x1=10]

(i) Which of the following expression is correct for

(a) (b)

(c) (d) None

(ii) Displacement density D is a

(a) Vector quantity (b) Scalar quantity

(c) Peak function (d) Periodic function

(iii) Magnetic vector potential (A) is given by

(a) (b)

(c) Both (a) & (b) (d) None

(iv) Select the wrong statement

(a) The tangential component of E is continuous but the tangential component of H is continuous at the surface of a perfect conductor

(b) The normal component of B is continuous at the surface of discontinuity but the normal component of D is continuous if there is no surface charge density

(c) The magnetic voltage around a closed path is equal to the electric current through the path

(d) Taking the divergence of amperes law yields the equation of continuity for steady currents.

(v) Uniform plane electromagnetic waves are

(a) Transverse in nature & have components of E & H only in the direction of propagation

(b) Transverse in nature & have components of E & H only in directions perpendicular to the direction of propagation

(c) Not transverse in nature

(vi) The ratio of total electric & magnetic field strengths i.e. have the dimensions of

(a) Impedance (b) Ohms

(c) (a) and (b) (d) None

(vii) The phase shift constant b is a measure of

(a) The phase shift in radians per unit length

(b) The phase shift per unit length

(c) The phase shift in radians

(d) The phase shift

(viii) Maxwells continuity equation for steady currents is given by

(a) (b)

(c) (d)

(ix) The capacitance of one conductor w.r.t. the neutral plane is

(a) Equal to the capacitance of the single phase line

(b) Half the capacitance of the single phase line

(c) Two times the capacitance of the single phase line

(x) The self GMD method is used to evaluate

(a) Inductance (b) Capacitance

(c) Inductance & capacitance (d) None of the above

Part B

(a) Obtain Neumanns formula.

(b) Explain the physical significance of curl & divergence. [2x5=10]

Section B

Q-2. (a) State and prove Poyntings theorem. Also give the interpretation of E x H.

(b) Explain the concept of magnetic vector potential (A) & derive the expression for it. [2x10=20]

Q-3. (a) State & explain Amperes work law in the vector differential form. Also give the interpretation of

(b) Derive the relation between E & H in a uniform plane wave. [2x10=20]

Q-4. (a) State Biot Savarts law & deduce from it an expression for the magnetic field intensity H at a point located at a distance of r meters from an infinitely long straight conductor carrying a current I amperes. [10]

(b) Write the Maxwells equations both in differential & integral forms for sinusoidally time-varying fields using phase or notation. [5]

(c) What are Poissons & Laplace equations? Write Laplace equation in Cartesian & spherical coordinates. [5]

 

Section C

Q-5. (a) Determine the inductance of a 1-phase transmission line consisting of three conductors of 215 mm radii in the go conductor & two conductors of 5 mm radii in the return conductor. The configuration of the line is shown in fig. below

(b) The three conductors of a 3-phase line are arranged in a horizontal plane & are 4 meters apart as shown in fig. below. The diameter of each conductor is 2 cm. Calculate the capacitance of conductor. [2x10=20]

Q-6. (a) Find if

(b) Derive the expression for the inductance of a coaxial cable. [2x10=20]

Q-7. (a) If a scalar potential is given by the expression. Determine the potential gradient

Also prove that the vector is irrotational.

(b) Explain the effect of earth on the capacitance of single phase & three phase transmission line. Also derive the capacitance of a three phase transmission line including the effect of earth. [2x10=20]

Q-8. (a) Explain the followings:

(i) Stokes theorem

(ii) Differential form of ohms law.

(b) Derive expression of the capacitance of a double circuit line for two configurations of conductors i.e. hexagonal spacing & flat vertical spacing. [2x10=20]