Download 2013

Code No: R21024
R10
SET - 1
II B. Tech I Semester Supplementary Examinations Dec - 2013
ELECTRO MAGNETIC FIELD
(Electrical and Electronics Engineering)
Time: 3 hours
Max. Marks: 75
Answer any FIVE Questions
All Questions carry Equal Marks
1. a) What is Divergence? State and prove the divergence theorem?
b) Explain electric field intensity and derive the expression for it?
2. a) Derive Poisson’s equation and Laplace’s equation.
b) Define dipole moment and torque on an electric dipole in an electric field?
3.
a) What is Capacitance? Get expressions for capacitance of parallel plate capacitors with
composite dielectrics.
b) Find the relative permittivity of the dielectric material present in a parallel plate capacitor if
i) S= 0.12 m2 , d = 80 µm , V0= 12 V, and the capacitor contains 1µJ of energy.
ii) the stored energy density is 100 J/m3 , V0= 200V, d= 45 µm.
4. a) Explain Magnetic field Intensity and Biot-Savart’s law?
b) Derive the relation between magnetic flux, magnetic flux density, and magnetic field
intensity.
5.
a) What is Ampere’s Circuital law and get the expression for point form of Ampere’s Circuital
law.
b) Derive Maxwell’s third equation, Curl(H) = Jc.
6.
a) Get the expression for force between two straight long and parallel current carrying
conductors and torque on a current loop placed in a magnetic field?
b) Consider a rectangular loop of dimension 1m by 2m and lies in a uniform field B0= -0.6ay +
0.8az T. The loop current is 4 mA. Calculate the total force and torque contribution for each
side.
7. a) Define Self-inductance and Mutual inductance? Determine the self-inductance of a solenoid.
b) What are permanent magnets? Write their characteristics and applications.
8. a) Write the Maxwell’s equations in point form and integral form.
b) Write the Faraday’s laws of electromagnetic induction.
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Code No: R21024
R10
SET - 2
II B. Tech I Semester Supplementary Examinations Dec - 2013
ELECTRO MAGNETIC FIELD
(Electrical and Electronics Engineering)
Time: 3 hours
Max. Marks: 75
Answer any FIVE Questions
All Questions carry Equal Marks
1.
a) Infinite uniform line charges of 5 nC / m lie along the (positive and negative) x and y axes in
free space. Find electric field intensity at i) A (0, 0, 4) m and
ii) B (0, 3, 4) m.
b) Derive the relation between force, electric field intensity, and potential acting between the
point charges with suitable example.
2.
a) State and explain Poisson’s Law for electrostatic fields.
b) Obtain expressions for electric potential and electric field intensity due to an electric dipole.
3.
a) Derive the boundary conditions between a conductor and a dielectric.
b) What is conduction and convection current? Derive the relations for conduction and
convection current densities?
4.
a) Find the expression for the magnetic flux density, ‘B’ at a distance ‘h’ above the centre of a
rectangular loop of wire ‘b’ meters on one side and ‘a’ meters on the other side. The loop
carries a current of one ampere.
b) A long solenoid has a radius of 2 cm and a length of 1.2 m. If the number of turns per unit
length is 200 and the current is 12 A, calculate the magnetic flux density i) at the Center and ii)
at the ends of the solenoid.
5.
a) Explain why Ampere’s circuital law is not applicable to determine the H for unsymmetrical
surfaces.
b) A circular loop located on x2 + y2 = 9, z = 0 carries a direct current of 10 A along a direction.
Determine H at (0, 0, 5)m and (0, 0, -5)m.
6.
a) State and explain Lorentz’s force equation?
b) A single-phase circuit comprises two parallel conductors A and B, each 5 cm diameter and
spaced 10 meter apart. The conductors carry currents of +50 and -50 amperes respectively.
Determine the magnetic field intensity at the surface of each conductor and also exactly
midway between A and B.
7.
a) Obtain the expression for inductance of a toroid.
b) Derive the expression for energy density in a magnetic field.
8.
a) Derive Maxwell’s fourth equation and explain its significance
b) Explain the terms: i) Motional EMF
ii) Static EMF
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Code No: R21024
R10
SET - 3
II B. Tech I Semester Supplementary Examinations Dec - 2013
ELECTRO MAGNETIC FIELD
(Electrical and Electronics Engineering)
Time: 3 hours
Max. Marks: 75
Answer any FIVE Questions
All Questions carry Equal Marks
1. a) State and explain Coulomb’s law to determine force between two point charges.
b) A charge of QA = -60 µC is placed at A(0,0,4) and a charge of QB = 100 µC is placed at B(0,3,4) in free space. If distance are in meters. Find the distance between AB. Find the force
exerted on QA by QB if 0 8 854 10 12 f / m
2. a) State and explain Laplace’s law for electrostatic fields.
b) Derive the expression for torque produced on the dipole present in an electric field.
3. a) State and explain the continuity equation.
b) Find the vector magnetic field intensity H at a point P (2.5, 2, 3) m caused by a current
filament of 12 A in aˆz direction on the z-axis extending from 0 to 6.
4.
a) A filamentary conductor is formed into an equilateral triangle with sides of length l, carrying
current I. Find the magnetic field intensity at the centre of the triangle.
b) A circuit having a direct current if 12 Amps, forms a regular hexagon inscribed in a circle of
radius 1.2 m. Calculate the magnetic flux density at the centre of the circular hexagon.
Assume medium to be free space?
5.
a) An infinitely long filamentary wire carries a current of 2 A along the z-axis in the positive zdirection. Calculate the B at (-3, 4, 7).
b) State and explain Lorentz force equation.
6.
a) Obtain the expression for force between two straight long and parallel current carrying
conductors.
b) Two conducting filaments extend along the ‘x’ and ‘y’ axes, carrying currents I1 and I2 in
the ax and ay directions, respectively. Find the differential force exerted on the differential
current element I2 dl2 at (0,1,0) m by the differential element I1 dl1 at (1,0,0) m.
7.
a) Explain the concept of vector and scalar magnetic potentials.
b) Derive the Neumann’s formulae for the calculation of self and mutual inductances.
8.
a) Explain about Poynting vector and discuss about its significance?
b) Explain about statically induced EMF and dynamically induced EMF? What is the
difference between them?
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Code No: R21024
R10
SET - 4
II B. Tech I Semester Supplementary Examinations Dec - 2013
ELECTRO MAGNETIC FIELD
(Electrical and Electronics Engineering)
Time: 3 hours
Max. Marks: 75
Answer any FIVE Questions
All Questions carry Equal Marks
1. a) Define Gauss’s law. Briefly write the applications of gauss’s law.
b) Derive the expression for electric field intensity at an arbitrary point due to a line charge
extending from negative infinity to positive infinity along the z-axis.
2. a) What is electric dipole? Obtain expression for torque on electric dipole in an electric field.
b) Briefly explain the behavior of conductors and insulators in an electric field
3. a) Obtain the expression for capacitance of a two-wire line.
b) A conducting cylinder with a radius of 1cm and at a potential of 20V is parallel to a
conducting plane which is at zero potential. The plane is 5cm distant from the cylinder axis.
If the conductors are embedded in a perfect dielectric for which εr= 4.5, find the capacitance
per unit length between cylinder and plane.
4. a) Explain magnetic field intensity due to circular and solenoid current.
b) Derive Maxwell’s second equation, div (B)=0.
5. a) Write Ampere’s current law and its applications.
b) Explain briefly about field due to a circular loop and square loops.
6. a) Explain about moving charges in a magnetic field- Lorentz force equation.
b) An electron with a a velocity u= (3 ax+12 ay- 4 az ) ×105 m/s experiences no net force at a
point in a magnetic field B=(10 ax+ 20 ay+30 az) mWb/m2. Find E at that point.
7. a) Explain about Vector magnetic potential due to simple configurations.
b) What are permanent magnets? Write their characteristics and applications.
8. a) Write the modifications of Maxwell’s equations for time varying fields.
b) Explain the terms
i) Displacement current
ii) Static and dynamically induced EMF’s.
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