College : Vardhaman College Of Engineering
Degree : B.Tech
Department : Electrical & Electronics Engineering
Semester : IV
Subject :Electro Magnetic Fields
Document type : Question Paper
Website : vardhaman.org
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Electro Magnetic Fields Question Paper :
VARDHAMAN COLLEGE OF ENGINEERING
Four Year B. Tech IV Semester Regular/Supplementary Examinations May – 2014
(Electrical and Electronics Engineering)
Date : 28 May, 2014
Time: 3 hours
Max Marks: 75
Answer ONE question from each Unit
All parts of the question must be answered in one place only
Related : Vardhaman College Of Engineering Electromagnetic Theory & Transmission Lines B.Tech Question Paper : www.pdfquestion.in/6338.html
Unit – I
1. a) Derive an expression for the potential at a point
b) Let a point charge 1 Q of 25 nC be located at p1 – 4, – 2, 7-
2. a) Explain the torque on an electric dipole in an electric field 8M
b) Point charges of 50nC each are located at A- 1, 0, 0- , B- 1, 0, 0-
Unit – II
3. a) State and explain Ampere’s circuital law. 7M
b) The magnetic field intensity is given in a certain region of space as
Find the total current passing through the
4. a) Obtain an expression for magnetic field intensity at a point
b) Mention the applications of Ampere’s circuital law.s – .
Unit – III
5. a) A spherical condenser has a capacitance of 54pF
b) A metal bar of conductivity is bent to from a flat 900 sector
Determine the resistance of the bar between the vertical curved surfaces
6. a) Obtain the boundary condition for electric field for conductor
b) Determine the self-inductance of a coaxial cable of inner radius
Unit – IV
7. a) Explain the concept of scalar and vector magnetic potential. 7M
b) A rectangular loop of wire in free space joins points A- 1, 0,1-
8. a) Briefly explain Lorentz force equation. 8M
b) A small current loop L1 with magnetic moment 5 z a A.m2
while another small loop current L2 with magnetic moment 3 z
Unit – V
9. a) Derive Maxwell’s equation from Faraday’s law. Also
write Maxwell’s equations for a general medium for time varying fields
b) If the electric field intensity in free space is given in the rectangular
Find the magnetic field intensity, H using Faraday’s law.
10. a) State and prove Poynting theorem.
Write the expression for average power density by using Poynting theorem.
b) The conduction current through a wire with a conductivity
find the displacement current. 6M
Unit – I :
1. a) Derive an expression for the potential at a point due to an infinite uniformly charged line.7M
b) Let a point charge 1 Q of 25 nC be located at p1 (4, – 2, 7) and a charge 2 Q ( 60 nC be at ( -2 p -3, 4, -2) . If 0 Q2=60, find E at p( 1, 2, 3) . 8M
2. a) Explain the torque on an electric dipole in an electric field 8M
b) Point charges of 50nC each are located at A (1, 0, 0) , B(1, 0, 0) , C(0,1, 0) , and D(0, -1, 0) in free space. Find the total force on the charge at A. 7M
Unit – II :
3. a) State and explain Ampere’s circuital law. 7M
b) The magnetic field intensity is given in a certain region of space as ? 2 ? / 2 2 / / y z H ? X ? y z a ? za A m . Find the total current passing through the surface z ? 4,1 ? x ? 2,3 ? y ? 5 , in the z a direction. 8M
4. a) Obtain an expression for magnetic field intensity at a point due to an infinite sheet of current. 7M
b) Mention the applications of Ampere’s circuital law. A long straight non-magnetic conductor of 0.2 mm radius carries a uniformly-distributed current of 2 A dc.Use Ampere’s circuital law to find H and B within the conductor, at radius ?. 8M
Unit – III :
5. a) A spherical condenser has a capacitance of 54pF. It consists of two concentric spheres differing in radii by 4cm and having air as dielectric. Find their radii.6M
b) A metal bar of conductivity is bent to from a flat 900 sector of inner radius a, outer radius b and thickness t as shown in figure. Determine the resistance ofthe bar between the vertical curved surfaces at ? ? a and ? ? b . 9M
6. a) Obtain the boundary condition for electric field for conductor and dielectric boundary.9M
b) Determine the self-inductance of a coaxial cable of inner radius a and outer radius b.6M
Unit – IV :
7. a) Explain the concept of scalar and vector magnetic potential. 7M
b) A rectangular loop of wire in free space joins points A(1, 0,1) to B(3, 0,1) to C(3, 0, 4) to D(1, 0, 4) to A. The wire carries a current of 6 mA, flowing in the azdirection from B to C. A filamentary current of 15 A flows along the entire z axis in the z a direction. Find F on side BC. 8M
8. a) Briefly explain Lorentz force equation. 8M
b) A small current loop L1 with magnetic moment 5 z a A.m2 is located at the origin while another small loop current L2 with magnetic moment 3 z i A.m2 is located at (4,-3,10). Determine the torque on L2 7M
Unit – V :
9. a) Derive Maxwell’s equation from Faraday’s law. Also write Maxwell’s equations for a general medium for time varying fields in differential and integral forms. 7M
b) If the electric field intensity in free space is given in the rectangular coordinates sin ? ?sin ? ? ? / ? m y E E ? x ?t ? z a v m . Find the magnetic field intensity, H ? using Faraday’s law. 8M
10. a) State and prove Poynting theorem. Write the expression for average power density by using Poynting theorem. 9M
b) The conduction current through a wire with a conductivity, 107 (S/m) and relative permittivity, er = 1 is given by 2sin ? ? c I ? ?t mA If 109 2 f Hz, find the displacement current. 6M