Anna University Examination May/June 2012 Important Questions ...

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