30-06-2012, 06:01 PM
ELECTROMAGNETIC WAVES AND TRANSMISSION LINES
[attachment=26385]
Introduction :
Electromagnetic theory is a discipline concerned with the study of charges at rest and in
motion. Electromagnetic principles are fundamental to the study of electrical engineering
and physics. Electromagnetic theory is also indispensable to the understanding, analysis
and design of various electrical, electromechanical and electronic systems. Some of the
branches of study where electromagnetic principles find application are:
Electric charge is a fundamental property of matter. Charge exist only in positive or
negative integral multiple of electronic charge, -e, e= 1.60 × 10-19 coulombs. [It may be
noted here that in 1962, Murray Gell-Mann hypothesized Quarks as the basic building
www.jntuworld.com
www.jntuworld.com
blocks of matters. Quarks were predicted to carry a fraction of electronic charge and the
existence of Quarks have been experimentally verified.] Principle of conservation of
charge states that the total charge (algebraic sum of positive and negative charges) of an
isolated system remains unchanged, though the charges may redistribute under the
influence of electric field. Kirchhoff's Current Law (KCL) is an assertion of the
conservative property of charges under the implicit assumption that there is no
accumulation of charge at the junction.
Electromagnetic theory deals directly with the electric and magnetic field vectors where
as circuit theory deals with the voltages and currents. Voltages and currents are integrated
effects of electric and magnetic fields respectively. Electromagnetic field problems
involve three space variables along with the time variable and hence the solution tends to
become correspondingly complex. Vector analysis is a mathematical tool with which
electromagnetic concepts are more conveniently expressed and best comprehended. Since
use of vector analysis in the study of electromagnetic field theory results in real economy
of time and thought, we first introduce the concept of vector analysis.
Vector Analysis:
The quantities that we deal in electromagnetic theory may be either scalar or vectors
[There are other class of physical quantities called Tensors: where magnitude and
direction vary with co ordinate axes]. Scalars are quantities characterized by magnitude
only and algebraic sign. A quantity that has direction as well as magnitude is called a
vector. Both scalar and vector quantities are function of time and position . A field is a
function that specifies a particular quantity everywhere in a region. Depending upon the
nature of the quantity under consideration, the field may be a vector or a scalar field.
Example of scalar field is the electric potential in a region while electric or magnetic
fields at any point is the example of vector field.
Co-ordinate Systems
In order to describe the spatial variations of the quantities, we require using appropriate
co-ordinate system. A point or vector can be represented in a curvilinear coordinate
system that may be orthogonal or non-orthogonal .
An orthogonal system is one in which the co-ordinates are mutually perpendicular. Nonorthogonal
co-ordinate systems are also possible, but their usage is very limited in
practice .
[attachment=26385]
Introduction :
Electromagnetic theory is a discipline concerned with the study of charges at rest and in
motion. Electromagnetic principles are fundamental to the study of electrical engineering
and physics. Electromagnetic theory is also indispensable to the understanding, analysis
and design of various electrical, electromechanical and electronic systems. Some of the
branches of study where electromagnetic principles find application are:
Electric charge is a fundamental property of matter. Charge exist only in positive or
negative integral multiple of electronic charge, -e, e= 1.60 × 10-19 coulombs. [It may be
noted here that in 1962, Murray Gell-Mann hypothesized Quarks as the basic building
www.jntuworld.com
www.jntuworld.com
blocks of matters. Quarks were predicted to carry a fraction of electronic charge and the
existence of Quarks have been experimentally verified.] Principle of conservation of
charge states that the total charge (algebraic sum of positive and negative charges) of an
isolated system remains unchanged, though the charges may redistribute under the
influence of electric field. Kirchhoff's Current Law (KCL) is an assertion of the
conservative property of charges under the implicit assumption that there is no
accumulation of charge at the junction.
Electromagnetic theory deals directly with the electric and magnetic field vectors where
as circuit theory deals with the voltages and currents. Voltages and currents are integrated
effects of electric and magnetic fields respectively. Electromagnetic field problems
involve three space variables along with the time variable and hence the solution tends to
become correspondingly complex. Vector analysis is a mathematical tool with which
electromagnetic concepts are more conveniently expressed and best comprehended. Since
use of vector analysis in the study of electromagnetic field theory results in real economy
of time and thought, we first introduce the concept of vector analysis.
Vector Analysis:
The quantities that we deal in electromagnetic theory may be either scalar or vectors
[There are other class of physical quantities called Tensors: where magnitude and
direction vary with co ordinate axes]. Scalars are quantities characterized by magnitude
only and algebraic sign. A quantity that has direction as well as magnitude is called a
vector. Both scalar and vector quantities are function of time and position . A field is a
function that specifies a particular quantity everywhere in a region. Depending upon the
nature of the quantity under consideration, the field may be a vector or a scalar field.
Example of scalar field is the electric potential in a region while electric or magnetic
fields at any point is the example of vector field.
Co-ordinate Systems
In order to describe the spatial variations of the quantities, we require using appropriate
co-ordinate system. A point or vector can be represented in a curvilinear coordinate
system that may be orthogonal or non-orthogonal .
An orthogonal system is one in which the co-ordinates are mutually perpendicular. Nonorthogonal
co-ordinate systems are also possible, but their usage is very limited in
practice .