Basic Electrical Engineering old question papers

• a) Classify types of consumers based upon their electricity consumption pattern. Also draw the single line diagram of a general power system.
• b) Find equivalent resistance at a-b Ra in the figure. Assume each element is 19. Le : 1 a ; 1 i fT bo

• a) Using nodal analysis to find v1, v2, and v3 in the following circuit. 3A a 82 sa@) 342 29 @ rv

OR

What are active and passive elements, unilateral and bilateral element? What is star delta transformation and writes its role in circuit analysis? = ———

• b) State superposition Theorem power theorem. Find voltage drop through 2-ohm resistor using Norton’s Theorem in given circuit. WY HORN noe cate eae "please Sem ve etceh Belin sR. : a ah Oe ae ae SSA: } “3 Re RE oles , fat a4 Pe pg Sew 2 :

• a) The waveform given is ‘the half wave rectified sine wave. Find the average, RMS value and form factor. Also find the amount of average power dissipated in 10 Q. v(t) 1O(V) [nnn wt or Tt 2a
• b) For the electric circuit shown below, find:
• i) supply current and branch currents
• ii) voltage across each branch
• iii) Active, reactive and apparent power of entire circuit
• iv) overall power factor
• v) Draw phasor diagram showing the currents and supply voltages. 4#Q 22 P 22 32 0000 OO00 10V

• a) With the help of series resonance curve, explain resonance in series RLC circuit. iiMerol ; i” b) Three identical coils, each of resistance 10 Q and inductance 42 mH = are connected a) in star b) in delta to a 415 V, 50 Hz, 3-@ supply. Determine: si i, line and phase currents
• ii) Line and phase voltages
• iii) the total power dissipated in each case and compare them.

• a) Explain two wattmeter method for three phase power measurement. Also, how it is different from one wattmeter and three wattmeter method,
• b) AS kVA, 200/1000 V, 50 Hz, single phase transformer gave the following test results: OC test: 200V, 1.2 A, 90 W SC test: 50 V, SA, 110 W : i. Calculate the parameters of the equivalent circuit referred to LV side.
• ii) Calculate the output secondary voltage when delivering 3 kW at 0.8 power factor lagging, the input voltage being 200 V. Find also the percentage voltage regulation.

• a) A250 V DC shunt motor takes 8 A line current on no load and runs at 1000 rpm. The resistance of the field winding and armature winding are 200 Ohm and 0.8 Ohm respectively. If the full load line current is 20 A, calculate the full load speed assuming constant air gap flux.
• b) Explain the construction of DC generator with working principle.

OR

Explain the importance of transformer in power transmission. Derive the EMF equation of transformer.

Write short notes on: (Any two) 2x5

• a) Speed Control of DC Motor
• b) Color coding of resistors
• c) Power in purely inductive circuit POKIIARA UNIVERSITY Level; Bachelor Semester: Fall Year =: 2023 Programme: BE Full Marks: 100 Course: Basic Electrical Engineering (New) Pass Marks: 45 Time 23 hrs. Candidates are required to give their answers in their own words as far as practicable, r——_ The figures in the margin indicate full marks. coM er oEnotes a ac errr rp 1. a)” With the help of single line diagram, explain generation, transmission, and distribution of electricity in Nepal.

OR

Explain the present energy scenario in Nepal. i bf Why do we need color coding of Resistors? Find the equivalent resistance of the following circuit. 40 A 40 40 rrr NS — 40 oul c iy _[ ° 40 40 BAYA \ NN 2. Determine the current in 5 Q resistor for the circuit shown using Superposition Theorem (Figure 22). 20 20V ; 50 30 10A 10 tov Figure 22 @ Calculate the value of R that will absorb maximum power from the circuit (shown in the figure). Also calculate the maximum power drawn by it. 102 f 252 4 cov @) 20Q 52

OR

Using mesh analysis, solve for li, 2, Is. 10V 4a@ 22 122 8V = C9 Determine the V; and V2 using Nodal Analysis method. Also determine the current flowing through 30 Q resistor (Figure 19) o_| oo S" wo + +V1- + V2 - : ov = + T 302 ~—s«6OV Figure 19 : : ies KL

• b) Find the average value, rms value of the voltage waveform given below. esi staid soni ah Beica ; ie Pe Nexis ale ae P| Qe 7 | Al See Ne a Tena nati 20S) oR) 4. a) What will be the case for resonance in series RLC circuit? Derive the resonant frequency for this case. (oy A circuit have following electrical components in parallel: a) a resistor of 500 ohm, b) an inductance of 2H, c) capacitor of microfarad. In this circuit 200V, 50 Hz source is applied. Calculate:
• i) the total current drawn from the supply
• ii) complex power ili. active power
• iv) reactive power
• v) power factor of the circuit Dp The star connected stator of three phase, 50 Hz alternator suppliesa balanced delta connected load. Each phase of the load consists of a coil of resistance of 15Q and inductance 36mH and the phase voltage generated by the alternator is 231V. Calculate: i, _ the phase and line currents,
• ii) the load power factor
• iii) the power delivered to the load.
• b) An ideal 25 KVA transformer has 500 tums on the primary winding and 40 turns on the secondary winding. The primary winding is connected to a 3.3 KV supply. Calculate:
• i) The secondary emf.
• ii) The primary and secondary currents on full load.
• iii) The maximum core flux. 6. a) .Explain the operation of transformer on load and also draw phasor diagram at lagging power factor. rH fp A 220 Volts de shunt motor draws a current of $ A, and runs witha 8 Ns speed of 1500 rpm at no-load. When the motdr is loaded, the speed drops to 1400 rpm. Calculate the current drawn by the motor at loaded condition. Given that the armature winding resistance is 0,2 and field winding resistance is 110 2. 7. Write short notes on: (Any two) 2x5 A Voltage divider Rule b)/ Sources of Energy . c) Operation of DC motors’ a