IMPORTANT QUESTIONS CO 1 1) Write short notes on : (a) Active and passive elements (b) Unilateral and bilateral elements (c) Linear and non-. (d) Ideal and practical source. 2) Derive the transformation between delta to star and star to delta. 3) Define: (a) Thevenin’s theorem (b) Norton’s theorem (c) Superposition theorem. 4) Find current through 2Ω resistance using (a) superposition theorem (b) Thevenin’s theorem (c) Norton’s theorem

5) Find current through 5 Ω using (a) Nodal analysis (b) Mesh analysis.

CO 2

6) The instantaneous value of two alternating are represented by 푉1 = 60 sin 휃 and 푉 = sin( 휃 − 휋). Derive the expression for the instantaneous values of (i) The 2 3 sum and (ii) the difference of these voltages 7) Two ac currents one represented as i1 = 25 sin (314 t + 200) & i2 = 35 sin (314 t + 450). Draw the phasor & show the resultant when they are connected in parallel. 8) A of 35 µF is connected in series with a variable . The circuit is connected across a 50 Hz main. Find the value of the resistor for a particular condition when the across the capacitor is half the supply voltage. 9) Derive expression of resonance frequency for series RLC circuit. A series circuit consists of a resistance of 10 Ω, and inductance of 50mH and a variable capacitance in series across a 100V, 50Hz supply. Calculate: (a) The value of capacitance to produce resonance. (b) Voltage across the capacitance (c) Q-factor. 10) Derive the relation between line current & phase current in case of three phase delta connected balanced load. Three identical coils of resistance 8Ω and inductive reactance 6Ω are connected in delta across 400V mains. Determine power, power factor and line current. Draw phasor diagram. 11) Explain power factor. What are the causes of low power factor? Explain methods of power factor improvement.

CO 3

12) Discuss the principle of operation of a single phase . Derive EMF equation for a single phase transformer. 13) Explain the different types of magnetic materials with examples. 14) Draw and explain the no load and full load phasor diagram for a single phase transformer. 15) Explain single phase auto transformer and give its application. 16) In a 25 KVA, 2000/200 V transformer, the constant and variable losses are 350 W and 400 W respectively. Calculate the efficiency on unity power factor at (i) Full load (ii) Half load 17) What is voltage Regulation in a single Phase Transformer? What should be its value for an ideal transformer? 18) Explain eddy current and B-H curve? 19) What are the advantages of auto-transformer over two winding transformer?

CO 4 20) Explain double field revolving theory for single phase induction motor. 21) Describe any one method of starting single phase induction motor with neat diagram. 22) Why synchronous motor is not self starting? 23) An 8 pole alternator runs at 750 rpm. It supplies power to a 6 pole, 3 phase induction motor, which has a full load slip of 3 %. Find the full load speed of the induction motor and the frequency of its rotor emf. 24) Derive the emf equation of dc generator. A 4-pole shunt generator with lap-connected armature has field and armature resistance of 50Ω and 0.1Ω respectively. If supplying power to 100W lamp load for 100 V. Calculate the armature current and the generated emf. Consider a contact drop of 1V per brush. 25) Derive the expression of torque for dc motor. Also discuss the application of it. CO 5 26) Draw the characteristics of battery. 27) What are the factors that affect the battery capacity? 28) Calculate the backup of battery of 100AH connected to load of 100 watts and supply voltage is 12V. 29) Write full form of (i) MCB (ii) MCCB (iii) ELCB (vi) SFU 30) What do mean by earthing? Explain any methods of earthing. 31) Write short notes on the following: (a) MCB (b) MCCB (c) Fuse (d) Types of wires 32) Why Earth pin is made thicker and bigger than line and neutral? 33) Calculate the energy consumption per day in a house using 5 CFLs of 20 W each, 3 fans of 60 W each for 3 hrs a day. 34) Explain the Requirement of earthing for electrical equipment. What is the difference between neutral and earthing? 35) Name the various cables used in electrical system based on insulation. Explain any two. What are the feature of good conductor in electrical circuit?