Les Flashcards
What happens when the divergence is taken from both sides of Ampère’s law?
Ampère’s law results in a contradiction.
Under what condition does the divergence of current density become zero in the continuity equation?
In static conditions.
How is Gauss’s law for displacement field derived?
By substituting electric charge density into the continuity equation.
What is required for electromagnetic waves to be explained and interpreted?
Solutions of the wave equations that also satisfy Maxwell’s equations.
What assumption is made for simplifying calculations of electromagnetic fields?
Fields are monochromatic and their time dependence is harmonic.
What is the relationship between electric and magnetic fields described by?
Structural equations.
What constitutes the basis of classical electrodynamics?
Maxwell’s equations and Lorentz force law.
What happens to the electromagnetic wave in a conductor with a very small conductivity?
The wave becomes attenuated.
What is the unit of electric current density?
Electric current density has units of A/m².
What is displacement current density derived from?
Time-varying electric field.
Fill in the blank: The Ampère-Maxwell law uses effective current density instead of ______.
J
What two types of currents are sources in the Ampère-Maxwell law?
- Conduction current
- Displacement current
What is the common characteristic of boundaries between a conductor and a dielectric?
The vertical component of the electric field must be continuous.
What happens to the tangential components of the electric field at the boundary between two dielectrics?
They are continuous.
What is the consequence of having a non-zero surface charge density at the boundary?
The vertical component of electric displacement is discontinuous.
What happens to the magnetic field component at the interface of a conductor and a dielectric?
It is discontinuous.
What is a special case for two dielectric materials at their interface?
No current density exists.
In a good conductor, what must be true about the vertical component of the electric field?
It must be zero.
What does the continuity equation imply for electric charge density?
It must satisfy the divergence condition.
True or False: The displacement current density can be neglected in quasi-static equations if the rate of change of the electric field is small.
True.
What is the result when applying the Ampère-Maxwell law to a closed loop that intersects two surfaces?
It predicts two different results.
What is the relationship between the wave equation and the electromagnetic wave propagation in a linear and homogeneous medium?
The wave equation describes the propagation of electromagnetic waves.
