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Electromagnetic Fields Question Paper - Dec 18 - Electrical And Electronics (Semester 3) - Jawaharlal Nehru Technological University (JNTUH)
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Electromagnetic Fields - Dec 18
Electrical And Electronics (Semester 3)
Total marks: 75
Total time: 3 Hours
Note:-
This question paper contains two parts A and B.
Part A is compulsory which carries 25 marks.
Part B consists of 5 units. Answer any one full question form each unit.
Each question carries 10 marks and may have a,b,c as sub questions.
1.a.
Define electrostatic field and mention nay two sources.
(2 marks)
00
1.b
Find the potential at Ra = 5m with respect to Rb= 15m due to point change Q=500 $\mu$C at the original and zero reference at infinity.
(3 marks)
00
1.c.
What are conductors and insulators? Give examples.
(2 marks)
00
1.d.
Define ohm law in point form.
(3 marks)
00
1.e.
Deduce the relation between magnetic flux, magnetic flux density.
(2 marks)
00
1.f.
Find the magnetic field intensity due to a current carrying conductor with finite length.
(3 marks)
00
1.g.
Explain Lorentz force equation.
(2 marks)
00
1.h.
Derive Numan's formula for mutual inductance.
(3 marks)
00
1.i.
State Faraday's law of electromagnetic induction.
(2 marks)
00
1.j.
Determine the EMF induced obout the path r=0.5,z=0,t=0. If B=0.01sin377t.
(3 marks)
00
PART-B
2.a.
Three equal positive charges of 4 x 10⁹ coulomb each ate located at three corners of a square, side 29cm , determine thee electric field intensity at the vacant corner point of the square.
(5 marks)
00
2.b.
State and explain Maxwell's first law.
(5 marks)
00
OR
3.a.
What is an electric dipole? Obtain expression for torque experienced by an electric dipole in a uniform electric field.
(5 marks)
00
3.b.
Derive the expression for Potential gradient.
(5 marks)
00
4.a.
Derive the expression for the energy stored in the charge condenser.
(5 marks)
00
4.b.
The capacitance of a parallel plate condenser ia 0.2$\mu$F. potential between the plate is 2V. Calculate the energy stored by the charged condenser.
(5 marks)
00
OR
5.a.
Differentiate static electric and magnetic field.
(5 marks)
00
5.b.
Derive equation of continuity. What is its significance?
(5 marks)
00
6.a.
Find the Magnetic field intensity due to a straight current carrying filament.
(5 marks)
00
6.b.
Find the magnetic field intensity at the centre O of a square loop of side equal to 5M and carrying 10A of current.
(5 marks)
00
OR
7.a.
State Ampere's circuital law and prove the same.
(5 marks)
00
7.b.
In the region 0<r<0.5m, in cylindrical co-ordinate ms , the current density is <img src="https://i.imgur.com/plJ6CDa.png" alt="enter image description here" /> and j=0 elsewhere. Use Ampere's law to find H.
(5 marks)
00
8.a.
Derive an expression for magnetic field strength. H, due to a current carrying conductor of finite length placed along the y-axis at a point P in x-z plane and r distant form the origin.
(5 marks)
00
8.b.
What is scalar magnetic potential? Give its limitations.
(5 marks)
00
OR
9.a.
A Toroid with cross section of radius 2cm has a silicon steel core of mean length 28cm and an air gap of length 1 mm. Assume tue air-gap is 10% greater than the adjacent core and find the mmf required to establish an air-gap flux of 1.5 mwb.
(5 marks)
00
9.b.
Explain the concept self and mutual inductance.
(5 marks)
00
10.
Write Maxwell's equations for static fields. Explain how they arr modified for time varying electric and magnetic fields.
(5 marks)
00
OR
11.a.
Generalized ampere's law for time varying fields.
(5 marks)
00
11.b.
In a material for which $\sigma$=5.0 s/m and $\epsilon$r= 1 , the electric field intensity is E= 250 sin1010t (V/m) . Find the conduction and displacement current densities and the frequency at which they have equal magnitudes.
(5 marks)
00
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