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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)

https://www.electrical4u.com/electric-current-and-theory-of-electricity/

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)




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)

2. Explain the relation between field theory and circuit theory in detail.

(A/M-17)

3. State Faraday’s Law of Electromagnetic induction.

(M/J-15)




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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