# RGPV Previous Question Papers BE 3rd Semester

# Electrical Circuit Theory

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**Engineering Model question paper 3rd semester, **

** Electrical & Electronics Engineering **

** PART – A**

**Answer all questions – Each question carries 4 marks**

(1) Compare and differentiate unilateral and bilateral systems. Can you apply reciprocity theorem to these?

(2) List the necessary conditions for driving point and transfer functions.

(3) Two coupled coils have K = 0.8, N1 = 500 turns, N2 = 1000 turns and the mutual flux being 0.9Wb, find the primary coil flux. If the primary current is 10A, find the primary coil inductance. Also obtain the secondary inductance.

(4) In a transformer, K = 0.8, the mutual inductance = 10 H, the no. of primary and secondary turns are 50 and 200. Obtain the value of the primary current to produce 0.5Wb flux to link with the secondary coil. Also, calculate the value of secondary current.

(5) State and explain Superposition theorem.

(6) 3 resistors R12, R23 and R31 are delta connected. Derive expressions for R1, R2 and R3 in equivalent star connected network.

(7) From basics obtain an expression for the potential difference between star point of the load and supply neutral. Can this be greater than supply line voltage? Explain

(8) Substantiate the statement “A polyphase system is like a multicylinder engine.”

(9) Explain how to develop a tieset matrix for a given graph.

(10) List out the applications of MATLAB.

(10 x 4 = 40 marks)

PART – B

Answer all questions – Each question carries 12 marks.

(11) Find the power dissipated in the 5? resistor shown in the figure below using mesh analysis. (12 marks)

OR

(12) Find the node voltages by node voltage analysis method. (12 marks)

(13) Write the mesh equations for the network shown in figure. (12 marks)

OR

(14) Find the drop across the capacitor and the resistor. (12 marks)

(15) Obtain the equivalent resistance for the network. All resistors are of 100????????? (12 marks)

OR

(16) Determine current through 3??resistor using Norton’s theorem for the network shown. (12 marks)

(17) The total power supplied to three similar resistors connected in (a) Y (b) from a balanced 3? source is P. One of the resistors burn out. (i) Derive the expressions for power in terms of P for both cases. Hence (ii) calculate the power taken from the supply system when three 100? non inductive resistances are connected in (a) Y (b) across a 400V, 50Hz, 3??mains. (iii) In the event one of the resistances burn out, what would be the value of total power taken from the mains in each of the two cases?

(12 marks)

OR

(18) Three impedances of ZR = 10 + j10 ??? ZY = 20 + j20 ??and ZB = 0 – j10 ?? are respectively star connected to a 3?, 400V symmetrical system of phase sequence RYB. Find (i) the star point potential (ii) voltage drop across each impedance (iii) the current in each supply line (iv) phase angle between the currents and corresponding line voltages (v) total real, reactive and apparent powers supplied to the load (vi) complete vector diagram of voltages and currents (vii) a balanced delta connected resistors which would take the same power. (12 marks)

(19) For the graph shown in figure below, Select a tree T {5,6,7,8,9}.Show all the fundamental cutsets Write down the cutset matrix. Obtain network equilibrium equation. How can these KCL equations be simulated in MATLAB? (12 marks)

OR

(20) With help of an example, show how P spice can be used for the electric circuit analysis. (12 marks)

(12 x 5 = 60 marks)