BSc Physics SEM V ATKT May 2017 ATKT PHYSICS IV ELECTRODYNAMICS Question Paper - Mumbai University | munotes

Questions asked in this paper

• (2) Figures to the right indicate full marks

1. Q1 (a) Attempt any one:
   • (i) Find the potential inside and outside a uniformly charged solid sphere 10 whose radius is R and total charge is q. Use infinity as your reference point. Compute the gradient of V in each region and check it yields the
   • (ii) A point charge q is held distance d above and infinite grounded 10 conducting plane, using method of image obtain the expression for
   • a) Potential V above the conducting plane
   • b) Force on charge q
   • (b) Attempt any one:
   • (i) Show that for electrostatic field curl E =0 5
   • (ii) Determine the electrostatic potential due to an infinite wire carrying a line 5 charge with linear charge density A, at a distance r from the wire
2. Q2 (a) Attempt any one:
   • (i) Starting from Biot-Savart’s law obtain expression for V. B and V X B 10
   • (ii) Explain the polarization and hence show that the potential of the polarized 10 object is that produced by volume charge density p, = plus
   • (b) Attempt any one: Show that there is no net charge induced in dielectric due to polarization of 5
   • (ii) a dipole P in a uniform electric field E show that net torque acting on 5 the dipole is N=P XE
3. Q3 (a) . Attempt any one:
   • (i) . What is magnetization? Give physical interpretation of surface and volume 10 bound currents. Why these currents are called as bound currents?
   • (ii) Explain the need to modify Ampere’s law. Obtain Maxwell’s modification 10 to Ampere’s law and show that modified form of Amperes law explain the problem of charging of capacitor Attempt any one:
   • (i) For linear. magnetic materials obtain the relation between magnetic 5 susceptibility permeability of material and permeability of free space
   • (ii) Ampere’s law in material in differential and integral form. 5
4. Q4 (a) Attempt any one:
   • (i) | Obtain Poynting work energy theorem in electrodynamics. What is 10 pointing vector S? Obtain continuity equation for S
   • (ii) A plane monochromatic electromagnetic wave is incident normally on the 10 boundary separating the two dielectric media. Calculate the amplitude of reflected and transmitted waves in terms of amplitude of incident wave Discuss the phase relationship of reflected and transmitted wave with the phase of incident wave
   • (b) Attempt any one:
   • (i) | Show that Newton’s third law appears to be violated in electrodynamics. 5 Explain how it is rescued
   • (ii) Obtain the average value of energy density and intensity of. plane 5
5. Q5 (a) Attempt any one:
   • (i) Determine the electric field due to potential, V = x? + + 4
   • (ii) Charge +2q and -3q are placed at a points A(O, 0, d) and B(O, 0, 2d) 4 respectively along the z- axis of an infinite earthed conducting plane placed along x-y plane. Find the force on the positive charge
   • (b) Attempt any one:
   • (i) A long narrow solenoid consist of 1000 turns per meter of its length, 4 carries 1.5 A current. Find the magnetic field inside the solenoid
   • (ii) Calculate the energy density in uniform electric field of intensity 8 V/m in 4 of dielectric constant 2.28
   • (c) Attempt any one:
   • (i) non-uniform magnetization of certain material is given by, 4 M = xyx+ 2yzy + 3zxz. Calculate the volume bound current density at the location (1, 1, 1). All quantities are in SI units
   • (ii) The magnetic susceptibility of linear medium is 2.8 x If an auxiliary 4 field H = A/m is applied to it along the z direction. Find the magnetization M and the magnetic field B. Assume = po = x 107
   • (d) Attempt any one:
   • (i) The average value of intensity of sunlight reaching the earth’s surface is 3 1300 Assuming sunlight reaching the earth’s surface to be plane and monochromatic, calculate the amplitude of electric field vector associated with it. Given: = 8.85 X C =3 X m/s
   • (ii) monochromatic electromagnetic wave is normally incident from 3 air (nj = 1) on glass (n2 = 1.5). Calculate the coefficient of reflection R and coefficient of transmission T

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