ARIES POLYTECHNIC COLLEGE, BNR PET CHITTOOR

DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING

SUBJECT :-ELECTRICAL CIRCUITS (EE303)             MAXIMUM MARKS :-80  QQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQ

PART A

NOTE  J Answer all the questions and each question carries three marks

             J Answer should be brief and straight to the point          

1. (A) state maximum transfer theorem?

    (B) Define active circuit and passive circuit with examples?

2. (A) Explain ideal voltage source and ideal current source?

    (B) State and explain Norton’s theorem?

3. (A) Define angular velocity and express the value in terms of frequency?

  (B)Explain the working of simple loop generator?

4. (A) The two vectors are Z₁ = 5-j2 and Z ₂ =-3-j8 perform (i) Z_{1 +} Z ₂ (ii) Z_{1 -} Z ₂

      (B) Perform the following operations

           (i) Convert 8+j6 into polar?    (ii) Convert 50<60⁰  into rectangular?

5 Three currents I₁ =20sin (wt); I ₂=15sin (wt+60⁰); I3=12sin (wt+120⁰) flowing in a circuit. Calculate the resultant current and express it in sinusoidal form?

6 (A) Define the term resistance, inductance and capacitance

   (B) Define Q factor of a parallel resonant circuit and write its formula

7 (A) what is resonant frequency and derive an expression for resonance frequency in series circuit?

   (B)Write down the difference between series and parallel resonant circuit?

8 Two circuit having impedances Z1 = 10-j15 and Z ₂ =-6-j8 are connected in parallel .If the total current supplied is 15A. What is the power taken in each branch?

9. State the advantages of poly phase system over single phase system?

10. (A) A balanced star connected load of (8+j6) per phase is connected to a 3 phase        230v supply. Find the line current, power and power factor?

   (B) Explain the term poly phase?

PART B

NOTE  J Answer any five  the questions and each question carries ten  marks

             J Answer should be brief and straight to the point         

1.(P)  A coil of resistance 5Ω and inductance 0.02H is connected in parallel with another coil of resistance   1Ω and inductance of 0.08 H .The circuit is connected to 100V,50HZ supply.

    Find (i) the supply current (ii) power factor of circuit.

  (Q) Three resistors each of 100Ω are connected in star to a 415V 50 Hz find the line current (a) with  given conditions (b)when three capacitors of each 100 micro Farad are shunted across each resistor

2 (P).Define (a) form factor (b) peak factor (c) average value (d) RMS value

  (Q) Perform the following operations and put the result in polar form (i) A+B (ii)A-B (iii)AXB (iv)A/B       where A=6+j8,B=3-j4 ?

3. (P) Derive transformation formula for deta to star transformation?

    (Q)Derive transformation formula for star to deta transformation?

4. (P) state and explain superposition theorem?

    (Q) Find the current through 20Ω resistance of network of fig 1. By using superposition theorem?

5. find the resistance between the X and Y of the networks shown in figure 2 and3

6.(P) Two coils X and Y are connected in series across a 240V, 50hz supply. The resistance of coil X is 5Ω and the inductance of coil Y is 0.015H.If the input from the supply is 3KW and 2KVAR. Find the inductance of coil X and resistance of coil Y.Calculate voltage across each coil.>

(Q) Show that in an   ac circuit containing pure inductance power is zero?

  7. (P) A resistance of 10Ω and inductance of 0.1H are connected in series across a supply of 220V, 50 Hz. Determine (a) The impedance (b) current flowing (c) power factor (d) the phase angle between V and I

(Q)A coil of resistance 5Ω and inductance 0.02H is connected in parallel with another coil of resistance 1Ωand 0.08H. The circuit is connected to 100V, 50Hz supply .Find (i) the supply current (ii) power factor of the circuit.

8. (P) State and explain Thevenins theorem?

    (Q) A series circuit, consisting of coil having a resistance of 30Ωand inductance of 0.5Hand a capacitor resonate at a frequency of 48hz.calculate the capacitance of capacitor which when connected in parallel with this circuit will increase the resonant frequency to 60 Hz?

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