EM Part 1 - 2 Flashcards
How can Faraday’s law in differential form (with curl) be written in terms of H (magnetic field intensity)?
What is the wave equation derivd from Ampere’s Law with damping?
What is the wave equation derived from Faraday’s Law with damping?
What are the two sets of wave equations with no losses (i.e. no damping)?
What are the phasor representations of the following equations (Maxwell’s Equations in differential form)?
What is the definition of a plane wave?
A plane wave is a configuration of electric and magnetic fields, which satisfy Maxwell’s equations and provide an approximation to physically observable electromagnetic waves.
What does a planar wavefront look like visually?
What does a spherical converging wavefront look like?
Why can plane waves be considered as ‘building blocks’ or time-varying electromagnetic fields?
In the same wy that time-harmonic (sinusoidal) signals are used in Fourier analysis, complicated electromagnetic fields can be represented by a superposition of plane waves.
What is the definition of wavefront?
Wavefront is defined as the locus of all points having the same phase at any given instant of time. In other words, it is an imaginary surface representing corresponding points of a wave that vibrate in unison.
The shape of the wavefront depends on the shape of the source of disturbance.
A wavefront is always normal to the light rays.
A wavefront does not propagate in the backward direction.
What is the equation for plane wave propagation in free space?
The term with σ is removed since it is equal to zero in free space.
What is the phasor corresponding to the following real vector function?
sine corresponds to negative j.
The phi term is a imaginary exponential because when cosine is converted into a exponential term the only term that does not have a time component is the
What is the intrinic impedance roughly equal to?
Is the intrinsic impedance an impedance in the traditional sense?
The intrinsic impedance is not a resistance in the sense of losses or dissipation. It is a quantity with dimensions of impedance and despite real in free space; it is not equivalent to resistance.
Transverse and longitudinal waves
What is the Poynting Vector?
The Poynting Vector is the instantaneous power density flow (at any point in space).
In other words, it represents the direction of propagation of an electromagnetic wave and the energy flux density (intensity) of that wave.
Problem 2D: Show that a plane wave of general elliptical polarization can be regarded as the superposition of two plane waves linearly polarized (one in the direction of x and the other in the direction of y) with the appropriate time phase difference.
Problem 2E: Show that an arbitrary elliptically polarized wave can be considered as the superposition of two counter-rotating circularly polarized waves.
How do you do the cross product again?
Main thing to remember is how the crossed out values move and the negative value for the second term.
