BASIC ELECTRICAL ENGINEERING


UTTARAKHAND TECHNICAL UNIVERSITY

B.TECH FIRST YEAR, 2012
 BASIC ELECTRICAL ENGINEERING


time : 3hr
Total marks :100
SECTION A
Q1:- Attempt any four of the following :
  1. Define the following
    (i)  Resistance
    (ii) Specific Resistance
    (iii) Potential difference
    (iv) Unilateral Element
    (v)  Ammeter
  2. In the circuit shown 100 V dc voltage is applied across terminal A-B, calculate the power dissipated in each resistor and the reading of a voltmeter connected across the 5 ohm resistor.
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  3. State and prove the maximum Power Transfer theorem.
  4. Using nodal method, find current through 100 ohm resistor.utu previous year
  5. Explain the conversion of current source into equivalent voltage source  for solving a problem.
SECTION B
Q2:- Attempt any two of the following :

  1. Find the equivalent impedance of the following impedances  connected in parallel
    Z1 = 8 + j6, Z2 = 8 -j6, Z3 = 8.66 + j5.
  2. For the following impedance   Z1 = 10 + j20, find its conductance and susceptance.
  3. What do you mean by resonance in a series ac circuit? What will be the power factor of series resonating circuit?
  4. A balance star connected load of 8 + j6 ohms per phase is connected to a 3-phase, 230 V supply. Find the line current, power factor , power, reactive volt amperes and total volt-amperes.
  5. A voltage of 250 V at 50 Hz is applied to the circuit shown below, find current drawn from the source.
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SECTION C
 Q3:- Attempt any two of the following :
  1. Draw the phasor diagram for a practical transformer under the condition that, a lagging power factor load is connected across its terminals.
  2. An iron ring of mean circumference 80 cm is made of iron of area 8 Cm2 .It has a cut of 2 mm wide and is wound with 500 turns. Find the current required to produce a flux of 0.8 mWb across the air-gap. Relative permeability of the iron is 1000.
  3. A transformer is rated at 100 kVA. at full load its copper loss is 1400 W and iron losses are 940 W. Calculate
    (i) The efficiency at full load, unity power factor.
    (ii) The efficiency at half load, same power factor.
    (iii) The load kVA at which maximum efficiency will occur.

SECTION D

 Q4:- Attempt any two of the following :
  1.  Explain the principle and construction of attraction type moving iron instruments. Discuss their merits and demerits?
  2. Draw the characteristics of a compound D C generator? An 8-pole lap connected armature has 40 slots generates a voltage of 500 V. Determine the speed at which it is running if the flux per pole is 50 mWb?
  3. Explain the principal of operation of a three phase induction motor? Draw its speed-torque characteristics.  
SECTION E
Q5:- Attempt any two of the following :
  1. Write short note on any two of the following?
    (i) Operation of stepper motor with diagram?
    (ii) Construction diagram and the working of Auto-transformer starter? 
  2. A 3 phase, 6 pole 50 Hz induction motor has a slip of 2% at no load and 3% at full load. Determine
    (i) Synchronous speed
    (ii) No load speed
    (iii) full load speed
    (iv) frequency of rotor current at standstill.
    (v) frequency of rotor current at full load.
  3. Is Synchronous machine a self starting motor? If not then explain the methods of starting of a synchronous motor?
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