ELECTROMAGNETICS ARIZONA STATE UNIVERSITY –
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EVALUATED 2026-2027 FINAL EXAM| HIGH YIELD
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SECTION 1: MAXWELL'S EQUATIONS AND ELECTROMAGNETIC THEORY
Question 1
Which of Maxwell's equations mathematically describes Faraday's law
of electromagnetic induction?
A) ∇ × H = J + ∂D/∂t
B) ∇ × E = -∂B/∂t
C) ∇ · D = ρv
D) ∇ · B = 0
B) ∇ × E = -∂B/∂t
The curl of the electric field intensity equals the negative time rate of
change of the magnetic flux density. This equation captures how a
time-varying magnetic field induces a circulating electric field, which
is the fundamental principle behind transformers, generators, and
inductors.
,Question 2
The equation ∇ · B = 0 signifies which fundamental property of
magnetic fields?
A) Magnetic fields are conservative
B) Magnetic monopoles do not exist
C) Magnetic fields always point north
D) Magnetic flux decreases with distance
B) Magnetic monopoles do not exist
The divergence of magnetic flux density being zero means magnetic
field lines always form closed loops with no beginning or end. This
implies that isolated magnetic charges (monopoles) have never been
observed, and magnetic flux entering any closed surface must equal
the flux leaving it.
Question 3
In a source-free region, the wave equation for the electric field is
derived by combining which equations?
A) Gauss's law and Ampere's law only
B) Faraday's law and Ampere's law with Maxwell's addition
C) Gauss's law for electricity and Gauss's law for magnetism
D) Only Faraday's law
B) Faraday's law and Ampere's law with Maxwell's addition
Taking the curl of Faraday's law and substituting Ampere's law with
displacement current yields the wave equation. This combination
shows how time-varying electric and magnetic fields sustain each
other to propagate through space as electromagnetic waves.
,Question 4
What is the physical significance of the displacement current term
added by Maxwell to Ampere's law?
A) It accounts for current flowing through conductors
B) It explains how time-varying electric fields produce magnetic fields
C) It represents static charge accumulation
D) It describes resistance in materials
B) It explains how time-varying electric fields produce magnetic fields
The displacement current density ∂D/∂t allows a time-varying electric
field to generate a magnetic field even in the absence of free charge
motion. This term completes the symmetry of Maxwell's equations
and enables electromagnetic wave propagation through vacuum.
Question 5
The continuity equation ∇ · J = -∂ρv/∂t is derived from which pair of
Maxwell's equations?
A) Faraday's law and Gauss's law for magnetism
B) Ampere's law and Gauss's law for electricity
C) Both curl equations
D) Both divergence equations
B) Ampere's law and Gauss's law for electricity
Taking the divergence of Ampere's law and substituting Gauss's law
for electricity yields the continuity equation. This mathematical
relationship expresses conservation of charge, showing that current
flowing out of a volume equals the rate of charge decrease within it.
, Question 6
In phasor form, Faraday's law is expressed as:
A) ∇ × E = -jωB
B) ∇ × E = jωB
C) ∇ × E = -ωB
D) ∇ × E = B/ω
A) ∇ × E = -jωB
Converting the time-domain equation to phasor form replaces ∂/∂t
with jω. The negative sign is preserved from the original equation,
indicating that the induced electric field opposes the change in
magnetic flux according to Lenz's law.
Question 7
Which material property determines the speed of electromagnetic
wave propagation in a medium?
A) Conductivity only
B) Permittivity and permeability
C) Permeability only
D) Resistivity and conductivity
B) Permittivity and permeability
The wave velocity is given by v = 1/√(με), where μ is permeability and
ε is permittivity. These two properties determine how electric and
magnetic fields interact with the medium, controlling how fast energy
propagates through it.