VALLIAMMAI ENGINEERING COLLEGE

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1 P a g e 2 Question Bank Programme Subject Semester / Branch : BE : EE6201-CIRCUIT THEORY : II/EEE,ECE &EIE UNIT-I PART-A 1. Define Ohm s Law (B.L.T- 1) 2. List and define Kirchoff s Laws for electric circuits. (B.L.T- 1) 3. An 1Φ 50 Hz ac supply system has the RMS values of 100V, 10 A. Examine the instantaneous value of voltage and current. (B.L.T- 3) 4. Summarize the classifications of Circuit elements (B.L.T- 2) 5. Analyze how are the following affected by change of frequency a) Resistance b) Inductive reactance. (B.L.T- 4) 6. Define ideal voltage source (B.L.T- 1) 7. Define active elements and passive elements. (B.L.T- 1) 8. Distuinguish between series and parallel circuit (B.L.T- 2) 9. Select the value of R1 and R2 when they are parallel with the following conditions. The current in R1 is twice the current flowing through R2 and the equivalent resistance of the parallel combination is 10/3Ω. (B.L.T- 5) 10.Point out the magnitude of currents in the Ammeter of resistance 10Ω (B.L.T- 4) 11.A resistance of 120Ω and a capacitive reactance of 250Ω are connected in series across an AC voltage supply. If a current of 0.9 A is flowing in the circuit calculate the power factor. (B.L.T- 3) 12.Measure the equivalent conductance G eq of the circuit shown below (B.L.T- 5)

2 P a g e 3 13.Two inductances L 1 =3mH and L 2 =6mH are connected in parallel. Analyse and infer L eq (B.L.T- 4) 14.Compose the equivalent resistance for the following combination of resistor and source current (B.L.T- 6) 15.Generalize the expressions for mesh current equations in matrix form (B.L.T- 6) 16.Define power factor. (B.L.T- 1) 17.Describe the term phasor (B.L.T- 1) 18.Differentiate active and reactive power in electrical circuits (B.L.T- 2) 19.How do you differentiate Power and Energy in Electrical Circuits? (B.L.T- 2) 20.Calculate the power absorbed by each of the elements in a given circuit. (B.L.T- 3) PART B 1. Interpret the current delivered by the source shown in the circuit below.

3 P a g e 4 (B.L.T- 2) 2. For the network shown below, label the current ratio (I1/I3) by applying mesh analysis. (B.L.T- 1) 3. Tabulate a) the equivalent resistances across the terminals of the supply, b) total current supplied by the source and c) power delivered to 16 ohm resistor in the circuit shown in figure (B.L.T- 1) 4. Analyze the mesh currents I1 and I2 for the given circuit shown below (B.L.T- 4)

4 P a g e 5 5. Determine the value of V2 such that the current through the impedance (2+j3) ohm is zero (B.L.T- 3) 6. Use Nodal Voltage method and estimate the power dissipated in the 10 Ω resistance on the circuit shown in the fig (B.L.T- 2) 7. (i) Derive and list the expressions for resistors in series and parallel (8 marks) (B.L.T- 1) (ii) Quote the Kirchoff s current law and prove it by using the definition of Current (8 marks) (B.L.T- 1) 8. Calculate loop currents by mesh analysis (B.L.T- 3)

5 P a g e 6 9. In a circuit consisting of two elements in series, the equations for voltage and current are i=28sin(314+60º) and e=180 sin 314t formulate and obtain a) the RMS value of the voltage and current b) the frequency c) the power factor d) the power e) the values of circuit constants. (B.L.T- 6) 10.Evaluate the current in each branch and total power consumed by the circuit. Assume E = 50 sin (ωt+45). (B.L.T- 5) UNIT-II PART-A 1. Explain how voltage source with a source resistance can be converted into an equivalent current source. (B.L.T- 4) 2. Analyse the current flowing through the resistors R1 and R3 if current through R2 is 1A (B.L.T- 4) 3. Calculate The Equivalent Current Source for a Voltage Source Of 10v In Series With A 60ohm Resistance. (B.L.T- 3) 4. Illustrate the equivalent voltage source for a current source of 15A

6 P a g e 7 when connected in parallel with 5 ohm resistance (B.L.T- 3) 5. Given that the resistors Ra, Rb and Rc are connected electrically in star. Formulate the equations for resistors in equivalent delta. (B.L.T- 6) 6. Three resistors Rab, Rbc and Rca are connected in delta. Re-write the expression for resistors in equivalent star (B.L.T- 6) 7. How will you express the Norton s equivalent circuit from Thevenin s equivalent circuit? (B.L.T- 2) 8. State Superposition theorem (B.L.T- 1) 9. Describe the theorem used in converting an electrical circuit into one equivalent resistance in series with voltage source (B.L.T- 1) 10.Identify the theorem used in converting an electrical circuit into one equivalent resistance in parallel with current source (B.L.T- 1) 11. State Maximum power transfer theorem (B.L.T- 1) 12.Define reciprocity theorem (B.L.T- 1) 13.A voltage source has internal impedance (4+j5) ohm. Measure the load impedance for Maximum power transfer (B.L.T- 5) 14. Is reciprocity theorem applied to the circuit having resistors, capacitors and diodes? Give your reason (B.L.T- 2) 15.Three resistors A,B and C are connected in parallel and takes 2.5 A,I B =2I C Interpret(a) I B and I C (b)the line voltage and (c)r B and R C (B.L.T- 2) 16. Describe the concept of current division in a circuit. (B.L.T- 1) 17.Using superposition theorem, calculate current in the circuit. (B.L.T- 3) 18.Discuss some applications of maximum power transfer theorem (B.L.T- 2) 19.Point out the limitations of superposition theorem? (B.L.T- 4) 20.Convince the purpose of star delta transformation. (B.L.T- 5) PART-B 1. Deduce the expressions for star connected arms in terms of delta connected arms and delta connected arms in terms of star connected arms (B.L.T- 5)

7 P a g e 8 2. Determine the Thevenin s equivalent for the figure and develop the Norton s equivalent from the same (B.L.T- 6) 3. Using star-delta transformation, in the following wheat stone bridge circuit of figure. Calculate i)the equivalent resistance between P&Q ii)the total current (iii)the current through the 18Ω resistor (B.L.T- 3) 4. Using source transformation, replace the current source in the circuit shown below by a voltage source and solve for the current delivered by the 50V source (B.L.T- 3) 5. Analyze the given circuit and obtain Norton s equivalent circuit (B.L.T- 4)

8 P a g e 9 6. (i) For the circuit shown below, express the voltage across (2+j5) Ω impedance by using Superposition theorem. (8 marks) (B.L.T- 2) (ii) Discuss in detail and prove that, in a pure resistive circuit,r L =R Th using Maximum power transfer theorem. (8 marks) (B.L.T- 2) 7. Give Thevenin s equivalent across the terminals AB for the circuit shown in figure below. (B.L.T- 2) 8. Using superposition theorem identify the current through (2+j3) ohm impedance branch of the circuit shown. (B.L.T- 1)

9 P a g e (i) Examine the value of RL so that maximum power is delivered to the load resistance shown in figure. (8 marks) (B.L.T- 1) (ii) Define and explain reciprocity theorem. (8 marks) (B.L.T- 1) 10.Examine and identify the maximum power delivered to the load in the circuit (B.L.T- 1) UNIT-III PART-A 1. Define mutual inductance. 2. Express the dot rule. 3. Calculate the total inductance of the circuit, if the coefficient of coupling(k) between the two coils 0.6 as shown in fig. (B.L.T-3) 4. Define quality factor of a series resonant circuit.

10 P a g e Illustrate the quality factor of a coil for the series resonant circuit consisting of R= 10 ohm, L= 0.1 henry and C= 10 micro farad.(b.l.t-3) 6. Define quality factor Q of a coil 7. Design the frequency response of double tuned circuit. (B.L.T-6) 8. Describe bandwidth of the circuit? 9. Define coefficient of coupling. 10.Design the frequency response of RLC series circuit. (B.L.T-6) 11.Give the expression which relates the self and mutual inductance. 12. Define bandwidth of a resonant circuit. 13.Give the applications of tuned circuits. 14.A series resonance circuit has a bandwidth of 20kHz and a quality factor of 40. The resistor value is 10k ohm. Evaluate the value of L of this circuit. (B.L.T-4) 15.When do you say that a given AC circuit is at resonance? 16. Analyse resonant frequency in terms of half power frequencies.(b.l.t-4) 17. Judge, When the power is maximum in the series resonance circuits? Why? (B.L.T-5) 18. Examine the maximum possible mutual inductance of two inductively coupled circuits with self inductance L 1 =25mH and L 2 =100mH. (B.L.T-3) 19. Compare the properties of series and parallel resonant circuits. (B.L.T-4) 20.Deduce the resonant frequency and quality factor for the circuit shown (B.L.T-5) PART-B 1. With neat illustration and necessary derivations, describe the linear transformer 2. Define and derive the mutual inductance and the coupling coefficient of the transformer with necessary illustration. 3. Impedance Z 1 and Z 2 are parallel and this combination is in series with an impedance Z 3 connected to a 100V, 50 Hz ac supply. Z 1 =(5-jX c ) ohm,

11 P a g e 12 Z 2 =(5+j0) ohm, Z 3 =(6.25+j1.25) ohm. Analyse the value of capacitance such that the total current of the circuit will be in phase with the total voltage. Find the circuit current and power. (B.L.T-4) 4. The switch in the circuit shown in fig is moved from position 1 to 2 at t=0. Evaluate the expression for voltage across resistance and capacitor, energy in the capacitor for t>0 (B.L.T-5) 5. For the circuit shown in fig., calculate the impedance at resonant frequency, 10Hz above resonant frequency, and 10Hz below resonant frequency (B.L.T-3) 6. Describe how to derive Q factor of parallel resonance 7. (i) For the circuit shown below, express the frequency at which the circuit resonates. Also calculate the voltage across the inductor at resonance and the Q factor of the circuit. (8 marks) (ii) The number of turns in two coupled coils are 500 turns, 1500 turns respectively. When 5A current flows in coil 1, the total flux in this coil is 0.6* 10-3 Wb and the flux linking the second coil is 0.3*10-3 Wb. Calculate L 1, L 2, M and K. (8 marks) (B.L.T-3) 8. (i) A coil having an inductance of 100mH is magnetically coupled to another coil having an inductance if 900mH. The coefficient of coupling

12 P a g e 13 between the coils is Predict the equivalent inductance if the two coils are connected in (4+4 marks) a) Series aiding and Series opposing b) Parallel aiding and Parallel opposing (ii) What are coupled circuits? Sketch the frequency response of a single tuned circuit and give the explanation of tuned circuits. (B.L.T-6) (8 marks) 9. For a series RLC circuit: Derive the condition for resonance, explain the frequency response and also obtain quality factor and bandwidth. (B.L.T-4) 10. Discuss the following (i) Co-efficient of coupling (8 marks) (ii) Tuned circuit (8 marks) UNIT-IV PART-A 1. Define Step function? 2. Describe an initial condition? 3. Define transient? 4. Describe steady state value? 5. List the periodic inputs? 6. Quote the term time constant of a transient response. 7. Give time constant of a RL & RC circuit. 8. Distinguish between free and forced response. 9. Describe about Critical damping? 10.Analyze the current given by I (t) = 5 4 e-20t (B.L.T-4) 11. Design the equivalent circuit at t=0+ for a capacitor with initial charge of of q=0. (B.L.T-6) 12. Develop an equivalent circuit for inductor and capacitor at t=0+ when there is no initial energy. (B.L.T-6) 13. A coil having a resistance of 10 KΩ and inductance of 50mH is connected to a 10 volts, 10KHz power supply. Calculate the impedance (B.L.T-3) 14. In a series RLC circuit, L=2H and C= 5uF. Calculate the value of R to give critical damping. (B.L.T-3) 15. Distinguish between transient response and steady state response of a circuit.

13 P a g e A series RL with R=100Ω and L=20H has a dc voltage of 200V applied through a switch at t=0. Assuming the initial current through the inductor at t=0 is zero, evaluate the current at t=0.5sec (B.L.T-5) 17. Define a two port network 18. Discuss z- and y- parameter of a typical four terminal network.( B.L.T-2) 19.Summarize h parameter and give its applications. 20. In a two port network, Z11=100Ω, Z21=120Ω, Z12=120Ω, Z22=50Ω. Calculate Y parameters. (B.L.T-3) PART-B 1. Express the step responses of RL and RC circuits. Compare their performances. 2. Give the expression for current response of RLC series circuit with sinusoidal excitation. Assume that the circuit is working in critical damping condition. 3. (i) A series RC circuit with R=5 KΩ and C=20uF as a constant voltage source of 100V applied at t=0; there is no initial charge on the capacitor. Examine the current i and charge q for t > 0 (8 marks) (ii) In the circuit given below, the switch has been in position 1 for sufficient time to establish steady state conditions. The switch is then moved to position 2.show the current transient (8 marks) (B.L.T-3) 4. (i) Analyze the expression for current transient when series RL circuit is excited by a sinusoidal source v=vm(sin ωt) at t=0 (8 marks) (B.L.T-4) (ii)a series RLC circuit with R=50Ω, L=0.1H and C=50uF as a voltage of 100V applied to it at t=0 through a switch. Evaluate the expression for a current transient. Assume initially relaxed circuit conditions (8 marks) (B.L.T-5) 5. (i) Using laplace transform analyze expression for i 1 and i 2 in the circuit shown below, when dc voltage source is applied suddenly. Assume that initial energy stored in the circuit is zero. (8 marks)( B.L.T-4)

14 P a g e 15 (ii) In the circuit shown below examine the expression for the transient current. The initial current is shown in the figure (8 marks) 6. In the circuit shown describe about the expression for current if the switch is closed at t=0 and the value of current at t=1ms. Assume initial charge on the capacitor is zero

15 P a g e In the series circuit shown in figure, the switch is closed on position 1 at t=0. At t=1ms, the switch is moved to position 2. Interpret the equations for the current in both intervals and draw the transient current curve. 8. A series RC circuit with R=100Ω and C=25uF is supplied with a source of 200Sin(500t) volt. Express the current in the circuit. Assume initial charge on the capacitor is zero. 9. (a) Examine the transient response of series RLC circuit with DC input using laplace transform. i. Derivee the necessary differential equation and solve. ii. Discuss the cases of over damping, Critical damping and under damping (b) In a T network shown in fig Z 1 =2 0, Z 2 =5-90, Z 3 =3 90, calculate the Z parameters (8 marks) (B.L.T-3) 10. (i) Evaluate the Z parameters for the circuit shown in fig (8 marks) (B.L.T-5)

16 P a g e 17 (ii) Express Y parameters of network shown in fig from Z parameters. (8 marks) UNIT-V PART-A 1. Describe the effect of power factor in energy consumptionn billing 2. List the advantages of 3Φ system over 1Φ 3. List out the methods of power measurement in 3Φ circuits 4. Give the distortion power factor equation of three phase circuits. 5. List out the methods of power measurement in 3Φ circuits. 6. Identify the voltage across Y and B in a 3 Φ balanced delta system with voltage across R and Y is V. Assume RYB phase sequence 7. Distinguish between unbalanced source and unbalanced load. 8. Give the equations for the phasor difference between the potentials of the delta connected networks. 9. A 3Φ 400V supply is given to a balanced star connected load of impedance 8+j6 ohms in each branch. Estimate the line current 10.A 3Φ motor can be regarded as a balanced Y load. A 3Φ motor draws 5.6kW when the line current is 18.2A. Estimate the power factor of the motor

17 P a g e In the measurement of three phase power using two wattmeter method, predict when both the wattmeter read same values, what is the value of power factor of the load? 12.Describe measurement of reactive power using wattmeter. 13.Three coils, each having resistance of 20Ω and an inductive reactance of 15Ω are connected in star to a 400V, 3Φ and 50Hz supply. Calculate a) line current, b) power factor and c) power supplied. (B.L.T-3) 14.Calculate the power factor if V(t)=V m sin(ωt-45 0 ) and I(t)=I m sin(ωt ) (B.L.T--3) 15. Calculate the power factor if V(t)=V m sinωt and I(t)=I m sin(ωt ) (B.L.T--3) (B.L.T-4) 16.Explain balance supply system. 17. In two wattmeter power measurement method, if one wattmeter reads zero, analyze the power factor of the circuit. (B.L.T-4) 18.Compare star and delta connected system. (B.L.T-4) 19. Summarize the main objectives of interconnection of the phases? (B.L.T-5) 20.Develop the circuit diagram for balanced delta connected load. (B.L.T-6) PART-B 1. Discuss in detail about the three phase 3-wire circuits with star connected balanced loads. 2. Explain in detail the phase diagram of voltages and currents of a three phase unbalanced loads. (B.L.T-5) 3. A symmetrical three phase three wire 440v supply to a star connected load. The impedance in each branch are =2+j3Ω, =1-j2Ω and =3+j4Ω. Calculate its equivalent delta connected load. (B.L.T-3) 4. A three phase balanced delta connected load of 3+j4Ω is connected across a 400v, 3 phase balanced supply. Examine the phase currents and line currents (Phase sequence in RYB). 5. A balanced delta connected load takes a line current of 15 A when connected to a balanced 3 phase 400 v system. A wattmeter with its current coil in one line and Potential coil between the two remaining lines read 2000W. Describes the load impedances. 6. Develop the expression for balanced delta connected load and draw the phasor diagram. (B.L.T-6)

18 P a g e Explain three phase power measurement by 2 wattmeter method for star and delta connected load and determine the power equation and draw the phasor diagram. (B.L.T-4) 8. Give the short notes on symmetrical components and un-symmetrical components. 9. The two wattmeter methods produces wattmeter readings P 1 =1560W and P 2 =2100W When connected to delta connected load. If the line voltage is 220V, Calculate (1) the per phase average power (2) the per phase reactive power. (3) the power factor (4) the phasor impedance. (B.L.T-3) 10. Describe about the various methods to measure the real power and power factor in the three phase circuits BLOOM S TAXONOMY PART A BTL 1 BTL 2 BTL 3 BTL 4 BTL 5 BTL 6 UNIT UNIT UNIT UNIT UNIT Total PART B BTL 1 BTL 2 BTL 3 BTL 4 BTL 5 BTL 6 UNIT UNIT UNIT UNIT UNIT Total