LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034
M.Sc. DEGREE EXAMINATION – PHYSICS
SECOND SEMESTER – NOVEMBER 2003
PH 2800 / PH 820 – ELECTRODYNAMICS I
28.10.2003 Max. : 100 Marks
1.00 – 4.00
PART – A
Answer ALL the questions. (10 x 2 = 20)
- Explain the statement that “electrostatic energy does not obey a superposition principle”.
- List any four basic properties of conductors in an electrostatic field.
- What are the two properties of an electrostatic potential which lead to a solution of Laplace’s equation in 3-dimensions?
- Define the Legendre polynomial by the Rodrigues formula and hence write down the 3rd order polynomial.
- Write down the expressions for the torque and the force on an electric dipole placed in an external electric field.
- State the relation between the applied electric field and the polarization vector in an anisotropic crystal.
- Define the surface current density and the volume current density in terms of the current .
- What is a linear magnetic material? State the relation between the magnetic permeability and susceptibility.
- State Faraday’s law of em induction in differential form.
- Give an expression for the Maxwell stress tensor.
PART – B
Answer any FOUR questions. (4 x 7.5 = 30)
- Find the energy of (a) a uniformly charged spherical shell and (b) a uniformly charged solid sphere. (3.5 + 4)
- A point charged is situated near an infinitely grounded conducting plane. By the method of electrical images, find the amount of induced charge.
- Derive an expression for the potential of an electrically polarized object in terms of bound charged.
- Explain the mechanism responsible for diamagnetism.
- Derive an expression for the mutual inductance of a pair of coils.
-2-
PART – C
Answer any FOUR questions. (4 x 12.5 = 50)
- a) Find the potential of a uniformly charged spherical shell of radius R for points outside and inside. (9)
- b) Check whether = is a possible electrostatic field
(k = a constant). (3.5)
- Obtain the multipole expansion of electrostatic potential of an arbitrary localized charge distribution. Also explain the term “dipole moment” of the distribution.
- Derive the Clausius – Mossotti formula which relates the polarizability to the dielectric constant.
- a) Explain the domain theory of ferromagnetism. (5)
- b) Bring out the Salient features of a hysteresis loop of ferromagnetic substance (7.5)
- a) Explain the potential formulation of electrodynamics.
- b) Explain the gauge transformation and bring out the differences between the Coulomb gauge and the Lorentz gauge
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