LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034  M.Sc. DEGREE EXAMINATION – PHYSICS

AC 12

FIRST SEMESTER – NOV 2006

         PH 1807 – ELECTRODYNAMICS

 

 

 

Date & Time : 28-10-2006/1.00-4.00           Dept. No.                                                       Max. : 100 Marks

 

 

 

PART A

Answer all questions                                                               (10 x 2 = 20)

 

1. Check whether the field given by is a
   possible electrostatic field or not
2. Distinguish between polar and non-polar dielectrics
3. Outline the characteristics of para magnetic materials
4. How are the bound and free charges related to each other in linear media?
5. State the Faraday’s law both in integral and differential form.
6. What is motional e.m.f
7. Define acceleration field?
8. What is anomalous dispersion?
9. Define the term skin depth?
10. Show that the power radiated by a point charge is proportional to the square of its
    acceleration.

 

 

PART B

Answer any four                                                                                 (4 x 7.5 = 30)

 

11. Derive Gauss’s law in integral and differential form
12. State Biot-Savart’s law. Hence find the magnetic field at a distance d from a long
    straight wire carrying a steady current (2 +5.5)
13. Show that the mutual inductance between a pair of coils is purely a geometrical
    quantity
14. A parallel plate capacitor is being charged. Using Maxwell’s relations, show that
    the rate at which energy flows into the capacitor from surrounding space is equal
    to the rate at which electrostatic energy increases  U =  pa².h.  e₀ E.  .
    Where a is the radius of the plates, h is the distance between the plates, e₀  is the
    permittivity of free space
15. Find the Charge and current distributions that will give rise to potentials V = 0,

with A =

 

• for >  ct

where  a is a constant and  c² = .

 

 

 

 

            PART C

Answer any four                                                                     (4 x 12.5 = 50)

 

 

16a) A point charge q is held at a distance d above an infinite grounded conducting
plane. Determine the amount of induced charge on the plane by the method of
images                                                                                                    (6.5)

1. b) Starting from an assembly of point charges, obtain an expression for the energy
   of volume charge in terms of electrostatic field.                                   (6)

17.a) Outline the theory of multipole expansion of magnetic vector potential (10)

1. b) Show that the torque on any steady current distribution in a uniform field
   is  ().

18.a) Discuss the potential formulation of electrodynamics

1. b) Explain Gauge transformations with reference to Coloumb and Lorentz Gauge
2. A plane electromagnetic wave is incident on a plane boundary between two non-
   conducting media. Specify the boundary conditions and hence derive Fresnel’s
   formula for the reflected and transmitted intensities.
3. Derive an expression for power radiated from a magnetic dipole

 

 

PART A                                                                            Answer all questions                                                            (10 x 2 = 20)

 

 

1. Does electrostatic energy obey the superposition principle?
2. Write down expressions for the electric field of continuous i) line charge and ii)
   volume charge distribution
3. How are the bound and free charges related to each other in linear media?
4. An electric field is defined E_z =  Calculate Curl   and divergence   .     Give the physical interpretation of the result
5. Find the magnetic field due to an infinite uniform surface current which is given
   by , covering the entire xy plane?
6. Define Maxwell’s stress tensor
7. A uniform magnetic field B is pointing up. Find the induced electric field, if B is
   changing with time
8. Magnetic forces do no work Prove this statement
9. Write down the boundary conditions when an electromagnetic wave passes from
   one medium to another
10. Write down Ampere’s law in differential form, with Maxwell’s modification

PART B

 

Answer any four                                                                                 (4 x 7.5 = 30)

 

11.a) Find the electric field at a distance z above the center of a flat circular disc of
radius R  carrying electric charge

1. b) Find the gradient of (i)  f(x,y,z) = x² + y³ + z⁴  and  (ii) f(x,y,z) = e^x sin y  ln z.

12.a) Establish an expression for the magnetic force on a segment of current carrying
wire                                                                                                        (3.5)

1. b) Calculate volume current density J due to current I distributed over a cylinder
   with radius R (Assume J varies with r  as J=Kr) (4)
2. Obtain an expression for the energy stored in a magnetic field
3. Discuss the propagation of plane monochromatic electromagnetic waves in a
   non-conducting media
4. What is Lienard-Wiechart potential. Find the potential of a point charge moving
   with constant velocity

 

 

 

 

 

 

 

 

 

 

 

 

 

PART C

 

Answer any four                                                                     (4 x 12.5 = 50)

 

16. Obtain the multipole expansion of potential of an arbitrary localized distribution
    of charge. Hence bring out the role of monopole and dipole terms with reference
    to shift of origin
17. a) Find the electric field produced by an uniformly polarized sphere of radius R
    (6)
18. b) A sphere of linear dielectric material is placed in an originally uniform electric
    field inside the sphere (6.5)
19. Define Poynting vector. Derive an expression for it?
20. Discuss the theory of propagation of plane electromagnetic waves when
    normally incident on the boundary of the two medium.
21. Obtain an expression for the power radiated from a electric dipole?

 

 

Go To Main Page

 

 

 

Latest Govt Job & Exam Updates:

View Full List ...