EM Questions Flashcards
2016 Paper 3 a)
2016 Question 3 b) i)
2016 - 3 - b - ii)
2016 - 3 - b - iii)
2016 - 4 - a - i)
2016 - 4 - a - ii), iii) iv)
Plane Waves: What is the exponential term called?
the phase factor
Plane Waves: How do you determine the magnitude of wave vector k?
Plane Waves: How do you determine the wavelength if you know the magnitude of wave vector k, and vice versa?
What does 1 over this square root of the vacuum permeability times the vacuum permittivity equal?
the speed of light.
Plane Wave Question - 2016 - 4 - b - a - all
Poynting vector question - 2016 - 4 - c - ii)
Time Harmonic Fields: How do you find the phasor forms of electric and magnetic fields?
The non-phasor forms have the imaginary components removed.
So if there is a cosine, you need to replace it with a negative exponential value wih the kr parameters as the exponent value.
Poynting Vector: What is the equation for time average dissipated power density
Poynting Vector question - 2016 - 4 - c - all
Polarization - 2016 - 5 - a)
The polarisation of an electromagnetic wave describes the form way in which the direction of the electric field varies in time at a fixed position. Linear polarisation refers to the case where the electric field direction is always along a fixed line. It occurs when the components of the field vary in phase. Elliptical polarisation refers to the case when the vector electric field describes an ellipse as time varies. It occurs when the field components are not in phase. Circular polarisation is a special case of elliptical polarisation when the ellipse is a circle. It occurs when the two t_ransverse components of the field have equal amplitude and are in phase quadrature._
What is the only requirement of linear polarization?
The electric field components are in phase.
Magnitude does not have to be the same.
What is the best way to determine the polarization when they give you values like this?
Draw an argand diagram.
Polarization - 2016 - 5 a) - all
Plane Waves: What is the intrinsic impedance of air?
Reflection and Refraction - 2016 - 5 - b - i) ii) iii)
Reflection and Refraction: Equation for a reflected electric and magnetic wave?
What is the conjugate of this result?
just change the sign of the exponent
What is a result of taking the conjugate of H in the time average power density equation?
The exponential terms cancel.
Reflection and Refraction - 2016 - 5 - b - iv) - vii)
Good conductors and good insulators: What are the conditions for a good conductor and a good insulator?
What are the cross products of these following values?
From this you need to remember that order matters when you are taking the cross product.
i x j = k
but
j x i = - k
TE and TM modes: What are the boundary conditions of a conductor?
on a conductor E tangential and H normal must be zero
TE Modes - 2016 - 6 - d - all
Is?
div curl F = 0
taking the divergence of a function that is being curled is always zero.
Poynting vector: Expression for the conservation of energy
State the meaning of each term and what the whole equation tell us.
The term in the l.h.s. represents the total power flowing into the volume V, the first term in the r.h.s. is the total dissipated power by Ohm’s effect inside the volume while the last term is the sum of stored electric and magnetic energy in the volume.
The equation shows that the total power coming into V is equal to the power dissipated inside the volume plus the rate of change (increase) of the total electric and magnetic energy stored in the volume.
Plane waves and Maxwells equations definitions - 2018 - 1 - all
Faradays law and Poynting Vectors - 2019 - q2 - all
a) is simply using the cross product, replacing the E terms with the dB/dt and then integrating
Reflection and Conductivity - 2018 - 3 - all
Question 2B Notes
Problem 2E Notes
Problem 2E
Recall the unit vector cross products
Polarization: How do you indicate the direction of rotation when visually showing the polarization of waves?
You indicate it with the time stamps for T.
Attached is an example of elliptical polarization with a anti-clockwise rotation.
What does n hat represent in this equation?
unit vector in the direction of propagation k.
k0 is the magnitude of k.
What is the dot product?
What is the dot product between two of the same unit vector?
dot product between the same unit vector is equal to 1.
e.g. unit vector (0 0 1)
(0 0 1) · (0 0 1) = 0*0 + 0*0 + 1*1
What is the complex conjugate of eix?
e-ix
