Basic Electrical Engineering - B.Tech 2nd Semester Examination, 2025

2025•Semester 3•Civil-CA•End Semester
Bihar Engineering University, Patna
B.Tech 2nd Semester Examination, 2025

Basic Electrical Engineering

Time: 03 HoursCode: 100212Full Marks: 70

Instructions:

  1. The marks are indicated in the right-hand margin.
  2. There are NINE questions in this paper.
  3. Attempt FIVE questions in all.
  4. Question No. 1 is compulsory.
Q.1 Choose the correct option/answer the following (Any seven question only):[14]

  1. Kirchhoff's Current Law is based on

    1. Conservation of momentum
    2. Conservation of magnetic flux
    3. Conservation of energy
    4. Conservation of charge

  2. In a bilateral element, voltage-current relation

    1. Changes with direction
    2. Same in both directions
    3. Constant
    4. Nonlinear

  3. Eddy current loss can be reduced by

    1. Thick laminations
    2. No laminations
    3. Thin laminations
    4. Magnetic shielding

  4. A circuit with low power factor draws

    1. Less current
    2. No current
    3. More current
    4. Zero reactive power

  5. Superposition theorem is not applicable to networks containing

    1. Nonlinear elements
    2. Dependent current source
    3. Dependent voltage source
    4. Transformers

  6. Transformer efficiency is maximum when

    1. Iron loss < Copper loss
    2. Copper loss > Iron loss
    3. Iron loss > Copper loss
    4. Iron loss = Copper loss

  7. A good solder joint should be

    1. Dull and grainy
    2. Thick and uneven
    3. Shiny and smooth
    4. Blackened

  8. Transformer works on

    1. AC only
    2. Both AC & DC
    3. DC only
    4. High voltage only

  9. Permeability is highest in

    1. Air
    2. Soft iron
    3. Wood
    4. Aluminum

  10. The rms value of a sinusoidal voltage with peak-to-peak value of 240 V is

    1. 84.86 V
    2. 94.68 V
    3. 77.82 V
    4. 89.15 V
Q.2 Solve both questions :[14]

  1. Determine the value of current flowing through the 10 \( \Omega \) resistor for given circuit:

    Question Diagram

  2. State and explain the Maximum Power Transfer Theorem, and derive the condition under which maximum power is delivered to the load.

Q.3 Solve both questions :[14]

  1. Define delta network and star network and derive the formulae to convert a delta network into its equivalent star network.

  2. A voltage wave has the variation shown in figure.
    (i) Find the average and effective values of the voltage.
    (ii) If this voltage is applied to a 10 \( \Omega \) resistance, find the dissipated power.

    Question Diagram
Q.4 Solve both questions :[14]

  1. A 100 W resistor is connected in series with a choke coil. When a 400 V, 50 Hz supply is applied to this combination, the voltages across the resistance and the choke coil are 200 V and 360 V respectively. Find the power consumed by the choke coil. Also, calculate the power factor of the choke coil and the power factor of the circuit.

  2. Define and find the expression for the condition of resonance, bandwidth and quality factor of a series R-L-C circuit.

Q.5 Solve both questions :[14]

  1. Derive the relationship between phase and line quantities (voltage, current) for a balanced three-phase delta-connected system. Also draw neat diagrams.

  2. Three similar coils each having a resistance of 10 \( \Omega \) and inductance of 0.04 H are connected in star across 3 phase, 50 Hz, 200 V supply. Calculate the line current, total power absorbed, reactive volt amperes and total volt amperes.

Q.6 Solve both questions :[14]

  1. Derive an emf equation for a single-phase transformer and explain voltage and current ratio of an ideal transformer.

  2. A 250 kVA, 50 Hz single-phase transformer has ratio of secondary to primary turns as 0.1. The secondary voltage at no-load condition is 240 V. Calculate (i) primary voltage and (ii) full load primary and secondary currents.

Q.7 Solve both questions :[14]

  1. Explain the working principle of DC generator and derive expression for the emf of a DC generator.

  2. Explain the working principle and operation of Three Phase Induction Motor.

Q.8 Solve both questions :[14]

  1. Explain the steps involved in proper soldering and desoldering of electronic components.

  2. Explain the difference between breadboard wiring and PCB wiring with advantages and limitations.

Q.9 Write short notes on any four of the following:[14]

  1. Residential and Commercial wiring systems.

  2. Superposition Theorem

  3. Hysteresis and Eddy Current losses

  4. Power factor improvement

  5. Power Triangle