Anna
University
Examination
May/June
2012
Important
Questions
Common
To
EC43:Electromagnetic
Fields
EC1253
Electromagnetic
Fields
080290021:Electromagnetic
Fields
147403:Electromagnetic
Fields
10144EC404:Electromagnetic
Fields
Note:
These
are
only
Important
questions
,
These
Question
May
Or
May
Not
be
Asked
for
University
Examination
Unit
I
1.Derive
the
expression
for
electric
Field
on
the
axis
at
a
point
h
m
of
a
uniformly
charged
circular
disc
of
radius
a
m
with
a
charge
density
of
ρ
s
c/m
2
2.
Find
the
electric
field
intensity
of
a
straight
uniformly
charged
wire
of
length
‘L’m
and
having
a
linear
charge
density
of
+ρ
C/m
at
any
point
at
a
distance
of
‘h’
m
3.
State
and
Prove
Gauss’s
law.
List
the
limitations
of
Gauss’s
law.
4.
Find
the
magnetic
field
density
at
appoint
on
the
axis
of
a
circular
loop
of
a
radius
b
that
carries
a
current
I
5
Explain
coulomb’s
Law
.three
equal
positive
charges
of
4X
10

9
coulomb
each
are
located
at
three
corners
of
a
square
,side
20cm.determine
the
electric
field
intensity
at
the
vacant
corner
point
of
the
square.
Unit
II
1.Circular
disc
of
radius
‘a’
is
uniformly
charged
with
a
charge
density
of
s
c/m
2
.
Find
the
electric
field
intensity
at
a
point
‘h’
from
the
disc
along
its
central
axis
2.
Derive
an
expression
for
magnetic
field
strength,
H,
due
to
a
current
carrying
conductor
of
finite
length
placed
along
the
y

axis,
at
a
point
P
in
x

z
plane
and
‘r’
distant
from
the
origin.
3.
Derive
the
expression
for
the
E
at
a
point
P
due
to
an
electric
dipole.
4.
Find
the
magnetic
field
intensity
at
the
centre
O
of
a
square
loop
of
sides
equal
to
5M
and
carrying
10A
of
current
Unit
III
1.Solve
the
laplace’s
equation
for
the
potential
field
in
the
hompogenous
region
between
the
two
concentric
conducting
spheres
with
radius
‘a’
and
‘b’
where
b>a
V=0
at
r
=
b
and
V
=V
0
at
r=a
.find
the
capacitance
between
the
two
concentric
spheres.
2.Determine
the
inductance
of
a
solenoid
of
2500
turns
wound
uniformly
over
a
length
of
0.25m
on
a
cylindrical
paper
tube
,
4
cm
in
diameter
.the
medium
is
air
3.
A
cylindrical
capacitor
consists
of
an
inner
conductor
of
radius
a
and
an
outer
conductor
of
radius
b.
The
space
between
the
conductors
filled
with
a
dielectric
whose
permittivity
ε,
the
length
of
the
capacitor
is
L.
Determine
the
capacitance
4.
Derive
an
expression
for
the
inductance
of
solenoid
5.Show
that
the
inductance
of
the
cable
L
=
µl/2π
(ln
b/a)
H.
6.Derive
an
expression
for
the
capacitance
of
a
spherical
capacitor
with
conducting
shells
of
radius
a
and
b.
Unit
IV
1.Solve
one
dimensional
Laplace’s
equation
to
obtain
the
field
inside
a
parallel
plate
capacitor
and
also
find
the
surface
charge
density
at
two
plates
2.State
and
prove
Poynting
theorem.
3.
Derive
Maxwell’s
equation
derived
from
Faraday’s
law
both
in
Integral
and
point
forms
4.
Three
capacitors
of
10,25
and
50
microfarads
are
connected
in
series
and
parallel.
Find
the
equivalent
capacitance
and
energy
stored
in
each
case
,when
the
combination
is
connected
across
a
500
V
supply
5.
Derive
modified
form
of
Ampere’s
circuital
law
in
Integral
and
differential
forms
Unit
V
1.Derive
the
expression
for
the
reflection
by
a
perfect
dielectric
–
normal
incidence
2.Obtain
the
wave
equation
for
a
conducting
medium
3.Derive
the
wave
equation
starting
form
Maxwell’s
equation
for
free
space
For
good
dielectrics
derive
the
expressions
for
α,
β,
ν
and
η.
4.
Find
α,
β,
ν
and
η.
for
Ferrite
at
10GHz
εr
=
9,
μr
=
4,
σ
=
10
ms/m
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