Exam Questions Papers - Engineering

Q1:

The inconsistency of Ampere's law can be removed by adding __________ to it.

A displacement current density alone.

B conduction current density alone.

C displacement and conduction current densities.

D none of these

ANS:A - displacement current density alone.

The ampere's law is given as ∇.H = J Taking divergence on both sides ∇.(∇xH) = ∇.J i.e., ∇.(∇xH) = ∇.J = 0 divergence of curl is always zero But ∇.J = -rv ... continuity equation. Hence the inconsistency. It can be removed as follows → Let ∇ x H = J + G where G is some unknown quality. Then ∇.(∇ x H) = ∇.(J x G) = 0 i.e. ∇.J + ∇.G = 0 i.e. ∇.J = -∇.G or ∇.G = (-rv) i.e. ∇.G = rv ...... Gauss's law in point form Differentiating on both sides. ∇.D = rv Comparing (i) and (ii), G = D Thus ∇ x H = J + D Where J is conduction current density and D is displacement current density which is added to remove the inconsistency of Ampere's law.