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Register

Number

Code

: 9EE-23

II

Semester

Diploma

Examination,

Nov./I)ec.

,2012

ELECTRICAL

&

ELECTRONICS

ENGINEERING

BOARI)

ELECTRICAL

CIRCUITS

Time:3Hours]

'

IMax.

Marks

:

100

Notes;.

(1)

Section-

I

is

compulsory.

@

Answer

any

two

full

questions

from

each

of

the remaining

Sections

-

II,

ilI

&

Iv.

SECTION

-

I

Fill

in

the

blanks

:

.

\

(i)

An

a.c.

current given

by

i

:

14.14

rin

(rt

*

J

nu,

an

nns

value

of

amDS.

(ii)

The

algebraic

sign

of

an

IR

drop

is primarily

dependent

upon

the

(iii)

The

superposition

theorem

is

essentially

based

on

the

concept

of

(iv)

The

force

experienced

by

a

current

carrying

conductor

lying parallel

to

a magnetic

field

is

._---_-.

(v)

Ohms

law of

magnetic

circuit

is

given

by_.

(b)

State and

explain

superposition

theorem.

SECTION

-

II

(a)

Define

active

circuit,

passive

circuit,

linear

circuit

and

non-linear

circuit.

(b)

Derive

an

expression

for

converting

star

network

into

delta

network.

4

6

[Turn

over

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4-

9EE-23

z

(c)

Find

the

magnitude

and

direction

of

current

through

the

battery

of

the

circuit

given

in

Fig.

1

by

applying

Kirchoffs

law.

vsllvrr

vr

ru

3.

(a)

(b)

(c)

D

Fig.

I

State

and

explain

Reciprocity

theorem.

Define

absolute

permeability

and

relative

units.

Using

superposition

theorem,

find

the

voltage

across

4

f)

shown

in

Fig.2

8C)

t2r)

permeability

and

0.5

C,

l6v

mention

their

in

the

circuit

0.25

A

4.

(a)

Define

the

following

and

mention

their

units

:

(i)

Magnetic

flux

(ii)

MMF

(iii)

Reluctance

(iv)

Magnetic

flux

density

Derive

an

expression

for

instantaneous

varue

in

terms

of

their

maximum

value.

A

wire

of

0.5

m long

carries

a

current

of

r00

amps

and

lies

at

right

angles

to

a

uniform

field

of

r.5

tesla.

Find

the

erectro

mechanical

force

on

the

conductor

when

the

direction

of

motio

i,

tii

;;;r;;;;;r;.1;

ii)

parallel

to

the

field

(iii)

inclined

at

30o

to the

direction

of

the

field.

(b)

(c)

F'ig.2

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(a)

(a)

(b)

(c)

(b)

(c)

(a)

(b)

(c)

(a)

(b)

SECTION

-

III

Mention

the

different

types

of

emfs induced

and

their

applications.

Derive an

expression for the energy

stored

in a magnetic

field.

Calculate

the inductance and energy

stored in

the magnetic

field

of an air

cored solenoid 50 crn long,

5 cm in

diameter

and wound

with

1000

tums,

if

carrying

a

current

of 5 Amps.

Define inductive

reactance

and capacitive

reactance

with

expression

and

mention their

units.

Explain how

ac

parallel circuits

can be

solved

by

vector method.

An/iron ring

of mean length 50 cm

has an

air

gap

of 1 mm

and

a

winding

of

300 turns. If

the relative permeabiliU

of iron

is

300 when

a

current

of

1 Amp flows

through the

coil,

find

the flux

density. Neglect

Fringing.

(a)

Define the

terms Amplitude,

cycle, Frequency,

Time period

and mention

their

units.

(b)

Define peak

factor

and form

factor

of an ac

circuit.

(c)

An

alternating

voltage

V

:200

sin 314

t

is applied

to a device

which

offers

an ohmic

resistance

of

20

f,

to the

flow of

current

in

the opposite

direction.

calculate the

rms value,

average

value

and form

factor

of

the current.

SECTION

_

IY

Define resonant

frequency

and

quality

factor

and mention

their

units.

IfA

:

(8

-j6)

A and

B

:

(3

+j4)

A, find

(i)

A

x

B

(ii)

A

+

B

in polar form.

Calculate

power

and

power

factor

of

an

R{

series

circuit.

State and

explain

Faradays

laws

of

electro magnetic

induction.

when

a

voltage

of

(150

+

j

1s0)

v

is

applied

to

a

circuit,

it

takes

a current

of

(5

-j4)

A. Find

(i)

Scalar

impedance

(ii)

Power

consumed

(iii)

Pf.

5

5

5

4

6

4

6

5

4

[Turn

over

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9EE-23

4

(c)

AseriesRLC

circuithasR:10

f),

L:0.1

H&C:100

pF andis

connected

across a200

V

variable frequency

source.

Find

(i)

Resonant

frequencY

(i0

Impedance

at this

frequencY

(iii)

The volta$o

drops

across

inductance

and capacitance

10.

(a)

Draw

a network

to show

how

three

phase system can

be connected

in Star

and

Delta.

(b) Derive

a relation

to calculate

3-phase

power and

power factor

by two

watt

meter

method.

(c)

A

three

phase star connected

load draws

a line

current

of 25'Amps.

The

load

kVA.

and

kW

are

20

and 16

respectively.

Find the reading

on each

of

the

two watt

meters

used to

measure

3

phase power.

7

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