EE-302

BOARD DIPLOMA EXAMINATION, (C-14)

MODEL PAPER

EE—III SEM EXAMINATION

Exam name : ELECTRICAL CIRCUITS      Time : 3 hours

[Total Marks : 80M]

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PART-A

10x3=30M

Instructions :-

1. Answer all questions. 
2. Each question carries three marks
3. Answers should be brief and straight to the point and shall not exceed five  simple sentences.

1) Define  active and passive circuit's.
2) Define Junction, branch & loop.
3) State superposition theorem.
4) Find relation between electrical degrees and mechanical degrees.
5) Define form factor &  peak factor.
6) Convert the following rectangular to polar form and polar to rectangular form.           i) 16 + j 12     ii)  50 L-600 .
7) The current flowing through a pure inductor is 20A ,find inductance  and power consumption when the voltage applied across is V = 200sin(314t).
8) why series renounces circuit is called  acceptor circuit.
9) State the condition for resonance in parallel circuit.
10) Three impedance each of 10 Ω Resistance, 5 Ω inductive reactance is connected in delta to a 400V 3 phase supply determine line current, power factor.

PART-B

12×5=60M

Instructions :

1. any five questions
2. Each question carries 12 marks.
3. Answers should be comprehensive and the criterion for valuation is the content but not the length of the answer.

11)  A) Derive transformation formula for star to delta transformation.
B) Determine equivalent resistance between AB.

12)   Find  the  current  in  each  resistor  using  Kirchhoff  law. 

13)  a)   State  thevenins theorem.

b) Find  the  value  of  R  for which  the  observed  power  will be  maximum  also  find maximum  power in  RL

14)  a) Determine  average  value  of  sinusoidal  wave.

b)  The  equation  of  an  alternating  current  is   I  = 42.42  sin  (628t)  Determine  its

i) RMS value

ii)  Average  value

iii) Frequency

iv)  Form  factor 

v) Peak  factor and determine average  value  of  sinusoidal wave.

15) A) Derive  the  formula  for Impedance,  Current,  Phase  angel, Power, Power factor in RL  series circuit. 

b)  A  coil  of  resistance  20ohm  and  an  inductance  of  20mH is connected  in  series with  100µF capacitor across 200V  supply  find  resonant  frequency.

16)   Two  inductive  impedance  A  &B  are connected  in  series.

A   has   R=5  ohm  ,   L=0.01H .

B  has   R=3  ohms   &  L=0.02H.

If  sinusoidal voltage  is applied  to  whole circuit calculate  impedance  of  each  coil  the  current  ,Power factor, voltage  drop  across each  coil   and  draw  vector diagram  .

17)   In  a  series parallel circuit shown  in  fig  the  parallel branch  A&B  are in  series with  C. The  impedance   are   ZA  =  (6  +  j5)  ZB =  (4  +  j3)  ZC=   (10  -  j7)  .  If  voltage  applied across the  circuit  is  200  V  at  50Hz.   Calculate  current  in  each  branch  and  total  current and   draw  vector diagram.

18)  a)   Prove  that  in  delta  connected  system  line  current  is  √3  times phase  current.

b)  A  3phase  50  Hz ,400V   induction  motor operated  on  full  load  with  an  efficiency of   85%   and power  factor of  0.85  .Calculate  the  readings of  two  watt  meters connected to  measure the  power in  the  motor.