DHANALAKSHMI COLLEGE OF ENGINEERING
DEPARTMENT OF EEE
EE6302-ELECTROMAGNETIC THEORY
UNIT – 4
PART A
1. Define mutual inductance and self inductance. (A/M-15)
Self inductance is the ration between the induced Electro Motive Force
(EMF) across a coil to the rate of change of current through this coil. Self
inductance is related term to self induction phenomenon.
Mutual Inductance is the ratio between induced Electro Motive Force
across a coil to the rate of change of current of another adjacent coil in such a way
that two coils are in possibility of flux linkage.
2. Distinguish between transformer emf and motional emf. (A/M-15)
``Induced emf'' is the more general term. By Faraday's Law, you get an
induced emf whenever there's a changing magnetic flux through a loop. ... But if
the changing magnetic flux were due to, say, an increasing current in a wire, you
wouldn't call it a ``motional'' emf.
3. State Faraday’s law of Electromagnetic induction. (M/J–16)
Faraday's law of induction is a basic law of electromagnetism predicting
how a magnetic field will interact with an electric circuit to produce an
electromotive force (EMF)—a phenomenon called electromagnetic induction.
4. What is meant by displacement current? (M/J–16)
In electromagnetism, displacement current is a quantity appearing in
Maxwell's equations that is defined in terms of the rate of change of electric
displacement field. Displacement current has the units of electric current
density, and it has an associated magnetic field just as actual currents do.
5. State Ohm’s law for magnetic circuits. (N/D-14)
ohm's law for magnetic circuits. Φ=mmf/R where Φ is the magnetic Flux,
mmf is the magnetomotive force, and R is the Reluctance.
6. State Faraday’s Law. (N/D-16)
Faraday's law of induction is a basic law of electromagnetism predicting
how a magnetic field will interact with an electric circuit to produce an
electromotive force (EMF)—a phenomenon called electromagnetic induction.
7) Differentiate transformer and motional emf. (A/M-17)
``Induced emf'' is the more general term. By Faraday's Law, you get an
induced emf whenever there's a changing magnetic flux through a loop. ... But if
the changing magnetic flux were due to, say, an increasing current in a wire, you
wouldn't call it a ``motional'' emf.
8) State: Poynting Theorem. (M/J-14)
This theorem states that the cross product of electric field vector, E and
magnetic field vector, H at any point is a measure of the rate of flow of
electromagnetic energy per unit area at that point, that is
P = E x H
Here P → Poynting vector and it is named after its discoverer, J.H. Poynting. The
direction of P is perpendicular to E and H and in the direction of vector E x H
PART B
1. Derive the Maxwell’s equations both in integral and point forms.
(A/M-17).(M/J-11),(N/D-11), (M/J-12),( N/D-12),( M/J-13),( M/J-14)( N/D-
14),( A/M-16)
3. State Faraday’s Law of Electromagnetic induction.
(M/J-15)
Faraday's law of induction is a basic law of electromagnetism predicting
how a magnetic field will interact with an electric circuit to produce an
electromotive force (EMF)—a phenomenon called electromagnetic induction.
4. Compare and explain conduction and displacement currents.
Conduction current is the electric current that flows through a conductor because
of an applied potential difference.
Displacement current ID is the current that is included to explain the magnetic field
inside the capacitor due to mounting up of charges on its plates.
Mathematically displacement current ID is expressed as the following:
Displacement current appears as a theoretical necessity in situations where non
steady current is encountered.
Example:
If we keep a magnetic needle between the plates of a charging capacitor
(incompletely charged) consisting of parallel plates shows a deflection indicating
that there exists a magnetic field between plates.
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