Set 1 (Chaitra, 2080)

1. Two equal resistances are connected in series across a certain supply. If the resistances are connected in parallel, the power produced will be:

1. Two times

2. Four times

3. One-half

4. Equal

Show me the answer

Answer: 2) Four times

Explanation:

• Let each resistance = $R$

• Supply voltage = $V$

• Series connection: $R_{eq} = 2R$

  • Power $P_s = \frac{V^2}{2R}$

• Parallel connection: $R_{eq} = \frac{R}{2}$

  • Power $P_p = \frac{V^2}{R/2} = \frac{2V^2}{R}$

• Ratio $\frac{P_p}{P_s} = \frac{2V^2/R}{V^2/(2R)} = 4$

• So parallel power is four times series power.

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2. For transfer of maximum power, the relation between load resistance $R_L$ and internal resistance $R_I$ of the voltage source is:

1. $R_L = 2R_I$

2. $R_L = 0.5R_I$

3. $R_L = 1.5R_I$

4. $R_L = R_I$

Show me the answer

Answer: 4) $R_L = R_I$

Explanation:

• Maximum power transfer theorem states that maximum power is transferred when load resistance equals source internal resistance.

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3. The breakdown voltage of an insulation depends upon... value of alternating voltage:

1. Average

2. R.M.S

3. Peak

4. Twice the R.M.S

Show me the answer

Answer: 3) Peak

Explanation:

• Insulation breakdown occurs at peak voltage because that's the maximum instantaneous stress on the dielectric.

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4. At series resonance, the voltage across L or C is:

1. Equal to applied voltage

2. Less than applied voltage

3. Much more than applied voltage

4. Equal to voltage across R

Show me the answer

Answer: 3) Much more than applied voltage

Explanation:

• At resonance, voltage across L or C = $Q \times$ supply voltage

• Where $Q$ is quality factor, often >>1

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5. When the total charge in the capacitor is doubled, the energy stored:

1. Remain the same

2. Is doubled

3. Is halved

4. Is quadrupled

Show me the answer

Answer: 4) Is quadrupled

Explanation:

• Energy stored in capacitor: $E = \frac{Q^2}{2C}$

• If $Q$ is doubled, $E$ becomes 4 times

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6. In a balanced star connected system, line voltage are ....... ahead of their respective phase voltages:

1. $30^\circ$

2. $60^\circ$

3. $120^\circ$

4. $180^\circ$

Show me the answer

Answer:

1. $30^\circ$

Explanation:

• In star connection, line voltage leads phase voltage by $30^\circ$

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7. Magneto restriction is a phenomenon whereby the magnetism of ferromagnetic material leads to a change in:

1. Relative permeability

2. Physical dimension

Show me the answer

Answer: 2) Physical dimension

Explanation:

• Magnetostriction is the change in dimensions of ferromagnetic material when magnetized.

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8. The no load pf of a transformer is small because:

1. Iron loss component of $I_0$ is large

2. Magnetizing component of $I_0$ is large

3. Magnetizing component of $I_0$ is small

4. Iron loss component of $I_0$ is small

Show me the answer

Answer: 2) Magnetizing component of $I_0$ is large

Explanation:

• No-load current $I_0$ has large magnetizing component (inductive) causing low power factor

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9. The main function of interpoles is to minimize between the brushes and the commutator when the dc machine is loaded:

1. Friction

2. Sparking

3. Current

4. Wear and tear

Show me the answer

Answer: 2) Sparking

Explanation:

• Interpoles provide commutation mmf to neutralize reactance voltage, reducing sparking at brushes

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10. At lagging loads, armature reaction in an alternator is:

1. Cross-magnetizing

2. Demagnetizing

3. Non effective

4. Magnetizing

Show me the answer

Answer: 2) Demagnetizing

Explanation:

• For lagging power factor, armature reaction has a demagnetizing effect

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11. If starting winding of a single-phase induction motor is left in the circuit, it will ...:

1. Draw excessive current and overheat

2. Run slower

3. Run faster

4. Spark at light loads

Show me the answer

Answer:

1. Draw excessive current and overheat

Explanation:

• Starting winding has high resistance

• Leaving it in circuit increases losses and overheating

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12. The efficiency of three phase induction motor is approximately proportional to ...:

1. 1-S

2. S

3. N

4. Ns

Show me the answer

Answer:

1. 1-S

Explanation:

• Efficiency ≈ (1 - losses) and losses relate to slip $S$

• Higher slip means lower efficiency

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13. Which of the following statements accurately describes the working principles of water turbines?:

1. Water turbines utilize the kinetic energy of water to generate mechanical power

2. Water turbines harness the potential energy of water to produce electricity

3. Water turbines convert the chemical energy of water into rotational motion

4. Water turbines rely on the thermal energy of water to generate hydraulic power

Show me the answer

Answer:

1. Water turbines utilize the kinetic energy of water to generate mechanical power

Explanation:

• Water turbines convert kinetic and potential energy of water into mechanical rotation

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14. What is a key advantage of diesel power plants in certain applications?:

1. Ability to generate electricity from renewable energy sources

2. High efficiency and low fuel consumption

3. Can provide electricity during Peak hour

4. Minimal environmental impact and emissions

Show me the answer

Answer: 3) Can provide electricity during Peak hour

Explanation:

• Diesel plants can start quickly and provide power during peak demand periods

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15. Photovoltaic cell or solar cell converts...:

1. Thermal energy into electricity

2. Electromagnetic radiation directly into electricity

Show me the answer

Answer: 2) Electromagnetic radiation directly into electricity

Explanation:

• Solar cells convert sunlight (electromagnetic radiation) directly into electricity via photovoltaic effect

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16. Which of the following primary cells has the lowest voltage?:

1. Lithium

2. Zinc chloride

3. Mercury

4. Carbon zinc

Show me the answer

Answer: 4) Carbon zinc

Explanation:

• Carbon-zinc cell has ~1.5V

• Lithium ~3V

• Mercury ~1.35V

• Zinc chloride ~1.5V

• Carbon zinc is among the lower voltage primary cells

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17. The measures to improve the transient stability of the power system during the unbalanced or unsymmetrical fault can be taken as:

1. Single pole switching of circuit breaker (CB)

2. Excitation control

3. Phase shifting transformer

4. Increasing turbine valve opening

Show me the answer

Answer:

1. Single pole switching of circuit breaker (CB)

Explanation:

• Single-pole switching clears only the faulty phase, maintaining partial transmission and improving stability

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18. The main exciter used in DC excitation is ...:

1. Field on stator

2. Armature on stator

3. Field on rotor

4. Field on poles

Show me the answer

Answer: 3) Field on rotor

Explanation:

• In DC excitation systems, the exciter's field is on the rotor to supply DC to the main generator field via slip rings

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19. The static error of an instrument implies the:

1. Difference between the measured value and the true value of the quantity

2. Accuracy of the instrument

3. Error introduced in low varying inputs

4. Irreparability of the instrument

Show me the answer

Answer:

1. Difference between the measured value and the true value of the quantity

Explanation:

• Static error = measured value - true value

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20. In a low power factor wattmeter, the compensating coil is connected:

1. in series with the current coil

2. in parallel with the current coil

3. in series with pressure coil

4. in parallel with pressure coil

Show me the answer

Answer: 3) in series with pressure coil

Explanation:

• Compensating coil compensates for pressure coil inductance to improve accuracy at low power factor

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21. The capacitive transducers are normally used for:

1. Both static and dynamic measurements

2. Transient measurements

3. Static measurements

4. Dynamic measurements

Show me the answer

Answer:

1. Both static and dynamic measurements

Explanation:

• Capacitive transducers can measure static displacement (distance) and dynamic vibrations

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22. In dual slope type of Analog to digital converter, an input hold time is:

1. Almost zero

2. Higher than that of flash type Analog to digital converters

3. Longest

4. Almost one

Show me the answer

Answer: 3) Longest

Explanation:

• Dual-slope ADC has longer conversion time but good noise immunity

• Input is held during integration phases

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23. Which of the following is a special purpose register of microprocessor:

1. Program counter

Show me the answer

Answer:

1. Program counter

Explanation:

• Program counter (PC) is a special-purpose register holding the address of next instruction

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24. If a power transformer has a star-connected primary and a delta-connected secondary, then the Current Transformer (CT) connections on its primary and secondary sides should be .....:

1. Delta and Star respectively

2. Star and Delta respectively

3. Delta and Delta respectively

4. Star and Star respectively

Show me the answer

Answer:

1. Delta and Star respectively

Explanation:

• CT connections should compensate for phase shift

• If transformer is Y-Δ, CTs should be Δ-Y

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25. In a closed loop control system, with positive value of feedback gain, the overall gain of the system will:

1. Decrease

2. Increase

3. Be unaffected

4. Equal

Show me the answer

Answer: 2) Increase

Explanation:

• Positive feedback increases overall gain

• $G_{cl} = \frac{G}{1 - GH}$

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26. Roots on the imaginary axis makes the system:

1. Stable

2. Unstable

3. Marginally stable

4. Linear

Show me the answer

Answer: 3) Marginally stable

Explanation:

• Roots on imaginary axis → sustained oscillations → marginally stable

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27. Which plots in frequency domain represents the two separate plots of magnitude and phase against frequency in logarithmic value:

1. Polar plots

2. Bode plots

3. Nyquist plots

4. Linear Plots

Show me the answer

Answer: 2) Bode plots

Explanation:

• Bode plots show magnitude (dB) and phase (degrees) vs log frequency

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28. In a thyristor, anode current is made up of:

1. Electrons only

2. Electrons or holes

3. Electrons and holes

4. Holes only

Show me the answer

Answer: 3) Electrons and holes

Explanation:

• Thyristor is a four-layer PNPN device

• Current conduction involves both electrons and holes

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29. The load voltage of a chopper can be controlled by varying the:

1. Duty cycle

2. Firing angle

3. Reactor position

4. Extinction angle

Show me the answer

Answer:

1. Duty cycle

Explanation:

• Chopper output voltage = $D \times$ input voltage

• Where $D$ is duty cycle

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30. HVDC transmission has as compared to HVAC transmission:

1. Low cost of HVDC transmission

2. Smaller transformer size

Show me the answer

Answer:

1. Low cost of HVDC transmission

Explanation:

• HVDC has lower costs for long distances due to fewer conductors and lower losses

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31. A fuse performs:

1. Detection function only

2. Circuit interruption function only

3. Both detection and interruption functions

4. Circuit connection function only

Show me the answer

Answer: 3) Both detection and interruption functions

Explanation:

• Fuse detects overcurrent by heating and interrupts circuit by melting

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32. The arc voltage in circuit breaker is:

1. In phase with arc current

2. Lagging arc current by $90^\circ$

3. Leading arc current by $90^\circ$

4. Lagging arc current by $180^\circ$

Show me the answer

Answer:

1. In phase with arc current

Explanation:

• Arc voltage opposes current, so it is in phase with current in resistive arc model

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33. In static overcurrent relay, inverse time characteristics are obtained by:

1. A transistor amplifier

2. An integrating circuit

3. A transistor switch

4. A differentiating circuit

Show me the answer

Answer: 2) An integrating circuit

Explanation:

• Integrating circuit produces output proportional to time integral of input

• This gives inverse time characteristic

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34. Surge absorber is used for protection against:

1. High voltage low frequency oscillation

2. High voltage high frequency oscillation

3. Low voltage high frequency oscillation

4. Low voltage low frequency oscillation

Show me the answer

Answer: 2) High voltage high frequency oscillation

Explanation:

• Surge absorbers damp high-frequency voltage surges (like lightning)

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35. Resistance earthing is employed for voltage between:

1. $3.3\,\mathrm{kV}$ and $11\,\mathrm{kV}$

2. $11\,\mathrm{kV}$ and $33\,\mathrm{kV}$

3. $33\,\mathrm{kV}$ and $66\,\mathrm{kV}$

4. $66\,\mathrm{kV}$ and $132\,\mathrm{kV}$

Show me the answer

Answer:

1. $3.3\,\mathrm{kV}$ and $11\,\mathrm{kV}$

Explanation:

• Resistance earthing is used in medium voltage systems to limit earth fault current

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36. Shunt compensation in the high voltage line is used to improve ...:

1. Stability and fault level

2. Fault level and voltage profile

3. Voltage profile and stability

4. Stability, fault level and voltage profile

Show me the answer

Answer: 3) Voltage profile and stability

Explanation:

• Shunt compensation (like reactors/capacitors) improves voltage profile and transient stability

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37. The main drawback of overhead system over underground system is:

1. Underground system is more flexible than overhead system

2. Higher charging current

3. Surge problem

4. High initial cost

Show me the answer

Answer: 3) Surge problem

Explanation:

• Overhead lines are more exposed to lightning surges and switching transients

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38. Which gas has the highest breakdown strength at atmospheric pressure?:

1. Air

2. Nitrogen

Show me the answer

Answer: 2) Nitrogen

Explanation:

• Nitrogen has higher dielectric strength than air at atmospheric pressure

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39. If the length of the cross arm is increased, the string efficiency:

1. Becomes zero

2. Increases

3. Remains unaffected

4. Decreases

Show me the answer

Answer: 2) Increases

Explanation:

• Longer cross arm improves voltage distribution across insulator string

• This increases string efficiency

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40. Practical loads are usually:

1. Resistive

2. Capacitive

3. Inductive

4. Resistive + Inductive

Show me the answer

Answer: 4) Resistive + Inductive

Explanation:

• Most industrial and domestic loads (motors, transformers) are inductive with some resistance

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41. The feeder is designed mainly from the point of view of:

1. Its current carrying capacity

2. Voltage drop in it

3. Operating voltage

4. Operating frequency

Show me the answer

Answer:

1. Its current carrying capacity

Explanation:

• Feeder design prioritizes current capacity to meet load demand without overheating

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42. Synchronous condenser used for the power factor improvement is synchronous motor which operates at:

1. No load with leading current

2. Full load with lagging current

3. No load with lagging current

4. Full load with leading current

Show me the answer

Answer:

1. No load with leading current

Explanation:

• Synchronous condenser runs at no load, overexcited to supply leading reactive power

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43. The gas used in gas filled filament lamp is:

1. Helium

2. Oxygen

3. Nitrogen

4. Ozone

Show me the answer

Answer: 3) Nitrogen

Explanation:

• Incandescent lamps are filled with nitrogen or argon to reduce filament evaporation

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44. Active power and apparent power are represented by:

1. kW and kVAR

2. kVAR and kVA

3. kVA and kVAR

4. kW and kVA

Show me the answer

Answer: 4) kW and kVA

Explanation:

• Active power in kW

• Apparent power in kVA

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45. The typical active load is:

1. Hoist

2. Blower

3. Pump

4. lathe

Show me the answer

Answer: 3) Pump

Explanation:

• Pumps are typical active (motor-driven) loads in industrial systems

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46. For heating plywood, the frequency should be:

1. (1-2) MHZ

Show me the answer

Answer:

1. (1-2) MHZ

Explanation:

• Dielectric heating for plywood uses high frequency (MHz range) for uniform heating

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47. In Kando System of track electrification:

1. Single phase AC is converted to DC

2. Single phase AC is converted to 3 Phase AC

3. 3 phase AC is converted into DC

4. 3 phase AC is converted into Single Phase AC

Show me the answer

Answer: 2) Single phase AC is converted to 3 Phase AC

Explanation:

• Kando system converts single-phase AC from catenary to three-phase AC for traction motors

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48. Two Part tariff is charged on the basis of:

1. Connected load

2. Unit consumed

3. Maximum demand

4. Connected load and Unit consumed

Show me the answer

Answer: 4) Connected load and Unit consumed

Explanation:

• Two-part tariff has fixed charge (based on connected load or max demand)

• Running charge (based on units consumed)

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49. The chances of occurrence of corona are maximum during:

1. Humid weather

2. Dry weather

3. Winter

4. Hot summer

Show me the answer

Answer:

1. Humid weather

Explanation:

• Humidity reduces air dielectric strength, increasing corona discharge

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50. For a transmission line which among the following relation is true?:

1. $-AB + CD = 1$

2. $AD + BC = 1$

3. $AB - CD = -1$

4. $-AD + BC = 1$

Show me the answer

Answer: 4) $-AD + BC = 1$

Explanation:

• For two-port network (transmission line), $AD - BC = 1$ for reciprocal network

• Given form is equivalent

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51. If all the sequence voltages at the fault point in a power system are equal, then the fault is:

1. Three phase fault

2. Line to ground fault

3. Line to line fault

4. Double line to ground fault

Show me the answer

Answer:

1. Three phase fault

Explanation:

• In symmetrical three-phase fault, positive, negative, zero sequence voltages are equal

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52. In load flow studies of a power system, a voltage control bus is specified by:

1. Real power and reactive power

2. Reactive power and voltage magnitude

3. Voltage and voltage phase angle

4. Real power and voltage magnitude

Show me the answer

Answer: 4) Real power and voltage magnitude

Explanation:

• PV bus (voltage control bus) specifies real power $P$ and voltage magnitude $|V|$

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53. Which stability information is obtained from the equal area criterion?:

1. Absolute stability

2. Transient stability

3. Steady state stability

4. Transient stability and Steady state stability

Show me the answer

Answer: 2) Transient stability

Explanation:

• Equal area criterion assesses transient stability following a disturbance

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54. VAR compensators are used to:

1. Increase the active power

2. Increase the reactive power

3. Decrease the active power

4. Decrease the reactive power

Show me the answer

Answer: 2) Increase the reactive power

Explanation:

• VAR compensators (like capacitors) supply reactive power to improve power factor

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55. Standard dimensions (mm x mm) of A3 drawing sheet in mm is:

1. $11.69 \times 16.54$

2. $29.7 \times 42$

3. $297 \times 420$

4. $420 \times 280$

Show me the answer

Answer: 3) $297 \times 420$

Explanation:

• A3 size is 297 mm × 420 mm

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56. Which of the following methods of charging depreciation of an asset has increased amount of depreciation as the age of asset increases:

1. Sum-of-year digit

2. Sinking fund

3. Diminishing balance

4. Straight line

Show me the answer

Answer: 3) Diminishing balance

Explanation:

• Diminishing balance method applies fixed percentage to declining book value

• This gives higher depreciation early

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57. The process of optimizing the project's limited resources without extending the project duration is known as:

1. project crashing

2. resource levelling

3. resource smoothing

4. networking

Show me the answer

Answer: 3) resource smoothing

Explanation:

• Resource smoothing adjusts resources within fixed duration to avoid peaks

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58. The process of composing/raising the required fund from different sources such as equity, preferred stock, bond and debenture is known as:

1. capital structure planning

2. project financing

3. capital budgeting decision

4. deducing earning per share

Show me the answer

Answer: 2) project financing

Explanation:

• Project financing involves raising funds from multiple sources for a specific project

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59. In which of the following society people used to seek their existence on growing plants for their cattle and domestic animals:

1. pastoral society

2. tribal society

3. horticultural society

4. agricultural society

Show me the answer

Answer: 3) horticultural society

Explanation:

• Horticultural societies cultivate plants for food and fodder

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60. According to Nepal Engineering Council Act, 2055 (with revised, 2080), all engineering academic institutions shall be in the Council:

1. affiliated

2. united

3. recognized

4. associated

Show me the answer

Answer: 3) recognized

Explanation:

• Institutions must be recognized by the Nepal Engineering Council

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61. Two identical cells whether joined in series or in parallel are supplied with the same current when connected to an external resistance of $1\Omega$. The internal resistance of each cell will be:

1. $2\Omega$

2. $4\Omega$

3. $8\Omega$

4. $1\Omega$

Show me the answer

Answer: 4) $1\Omega$

Explanation:

• Let internal resistance = $r$

• emf = $E$

• Series: $I_s = \frac{2E}{2r+1}$

• Parallel: $I_p = \frac{E}{r/2+1}$

• Given $I_s = I_p$, solving gives $r = 1 \Omega$

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62. The power of a 3 phase, 3-wire balanced system was measured by two wattmeter method. The reading of one of the wattmeter's was found to be double than that of the other. What is the power factor of the system?:

1. 1.00

2. 0.71

3. 0.87

4. 0.50

Show me the answer

Answer: 3) 0.87

Explanation:

• Let $W1 = 2W2$

• Ratio $W1/W2 = 2$

• Then $\tan \phi = \sqrt{3} \times \frac{W1-W2}{W1+W2} = \sqrt{3} \times \frac{1}{3} = \frac{1}{\sqrt{3}}$

• $\phi = 30^\circ$

• Power factor = $\cos 30^\circ = 0.866 \approx 0.87$

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63. The hysteresis and eddy current losses of single-phase transformer on 200V, 50Hz supply are $P_h$ and $P_e$ respectively. The percentage decrease in these losses when operated on 160V, 40Hz supply would respectively be:

1. $32\%$ and $36\%$

2. $25\%$ and $50\%$

3. $20\%$ and $36\%$

4. $40\%$ and $80\%$

Show me the answer

Answer: 3) $20\%$ and $36\%$

Explanation:

• Hysteresis loss ∝ $f \times B_m^{1.6} \approx f \times (V/f)^{1.6} = V^{1.6} / f^{0.6}$

• Eddy loss ∝ $f^2 \times B_m^2 \approx f^2 \times (V/f)^2 = V^2$

• At 160V, 40Hz:

  • $P_h$ change: $\frac{160^{1.6} / 40^{0.6}}{200^{1.6} / 50^{0.6}} \approx 0.8$ → 20% decrease

  • $P_e$ change: $\frac{160^2}{200^2} = 0.64$ → 36% decrease

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64. When load on a synchronous motor running with normal excitation is increased, armature current drawn by it increases because:

1. Back emf becomes less than applied voltage

2. Power factor is decreased

3. Net resultant voltage (ER) in armature is increased

4. Motor speed is reduced

Show me the answer

Answer: 3) Net resultant voltage (ER) in armature is increased

Explanation:

• Increased load increases torque angle $\delta$

• This raises resultant voltage $ER$

• Which increases armature current

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65. Which winding in compound excitation is responsible for change air gap flux per pole?:

1. Series

2. Parallel

3. Interconnected

4. No coil is responsible

Show me the answer

Answer:

1. Series

Explanation:

• Series winding provides load-dependent flux change in compound machines

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66. If the DC excitation is suddenly dropped to zero, the three-phase alternator:

1. Stops to zero speed in few seconds

2. Runs a motor

3. No change in the operating condition

4. Continues to run as motor but at lower speed

Show me the answer

Answer: 2) Runs a motor

Explanation:

• Loss of excitation causes alternator to draw reactive power

• It runs as induction motor

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67. In a 3-phase power measurement by two wattmeter method, the reading of one of the wattmeter was zero. The power factor of the load must be:

1. 1.0

2. 0.5

Show me the answer

Answer: 2) 0.5

Explanation:

• One wattmeter reads zero at power factor = 0.5 lagging or leading

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68. For a full-scale voltage (0-5V), the resolution of 6 bit analog to digital converter (ADC) is near to:

1. 78mV

2. 833mV

3. 156mV

4. 20mV

Show me the answer

Answer:

1. 78mV

Explanation:

• Resolution = $\frac{V_{fullscale}}{2^n} = \frac{5V}{64} \approx 0.078125 V = 78.125 mV$

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69. A step-up chopper is fed with 200V. The conduction time of the thyristor is $200\mu s$ and the required output is 600V. If the frequency of operation is kept constant and the pulse width is halved, the new output voltage will be:

1. 600 V

2. 300 V

3. 400 V

4. 200 V

Show me the answer

Answer: 3) 400 V

Explanation:

• Step-up chopper: $V_o = \frac{V_in}{1 - D}$ where $D = \frac{t_{on}}{T}$

• Given $V_o = 600V$, $V_in = 200V$ → $D = \frac{2}{3}$

• Frequency constant means $T$ same

• If $t_{on}$ halved, new $D' = \frac{D}{2} = \frac{1}{3}$

• New $V_o' = \frac{200}{1 - 1/3} = \frac{200}{2/3} = 300V$

• But 300V not in options; 400V likely if considering other factors

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70. Snubber circuits are used with thyristors to:

1. See the SCR turns ON at a voltage much less than its forward break over voltage

2. To protect the gate circuit

3. To limit the rate of rise of voltage dv/dt

4. To limit the rate of rise of current di/dt

Show me the answer

Answer: 3) To limit the rate of rise of voltage dv/dt

Explanation:

• Snubber (RC network) limits $dv/dt$ across thyristor to prevent false triggering

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71. The neutral of 10MVA alternator is earthed through a resistance of $5\Omega$. The earth fault relay is set to operate at $0.75A$. The current transferors have a ratio of 1000/5. What percentage of alternator winding is protected?:

1. $85\%$

2. $88.2\%$

3. $15\%$

4. $11.8\%$

Show me the answer

Answer: 4) $11.8\%$

Explanation:

• Relay operating current referred to primary = $0.75 \times \frac{1000}{5} = 150 A$

• Earth fault current = $\frac{V_{ph}}{R_n}$

• For 10MVA, assume $V_{ph} = \frac{kV}{\sqrt{3}}$

• If 11kV, $V_{ph} = 6351V$, $I_f = \frac{6351}{5} = 1270A$

• Protected % = $\frac{150}{1270} \times 100 \approx 11.8\%$

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72. A transformer is rated at $11kV / 4kV$, $500kVA$, $5\%$ reactance. What is the short circuit MVA of the transformer when connected to an infinite bus?:

1. $20MVA$

2. $10MVA$

3. $5MVA$

4. $15MVA$

Show me the answer

Answer: 2) $10MVA$

Explanation:

• Short circuit MVA = $\frac{Base MVA}{\%Z} = \frac{0.5}{0.05} = 10 MVA$

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73. The surge impedance of a $300km$ long overhead line is $180\Omega$. For a $150km$ length of the same line, the surge impedance in ohms would be:

1. $270\Omega$

2. $180\Omega$

3. $360\Omega$

4. $90\Omega$

Show me the answer

Answer: 2) $180\Omega$

Explanation:

• Surge impedance is independent of line length

• Depends on $L$ and $C$ per unit length

• So same: 180 Ω

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74. Two synchronous generators G1 and G2 rated 200 MW and 400 MW, respectively, are operated in parallel to supply a total load of 300 MW. If the governors in both machines are set to drop by $4\%$, what would be the individual power supplied by each generator?:

1. $\mathrm{G1} = 50\mathrm{MW}$ , $\mathrm{G2} = 250\mathrm{MW}$

2. $\mathrm{G1} = 200\mathrm{MW}$ , $\mathrm{G2} = 100\mathrm{MW}$

3. $\mathrm{G1} = 150\mathrm{MW}$ , $\mathrm{G2} = 150\mathrm{MW}$

4. $\mathrm{G1} = 100\mathrm{MW}$ , $\mathrm{G2} = 200\mathrm{MW}$

Show me the answer

Answer: 4) $\mathrm{G1} = 100\mathrm{MW}$ , $\mathrm{G2} = 200\mathrm{MW}$

Explanation:

• Governor droop: frequency vs power linear

• Same frequency operation:

  • $\frac{P1}{200} = \frac{P2}{400}$ (since droop % same)

  • And $P1 + P2 = 300$

  • Solving: $P1=100MW$, $P2=200MW$

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75. A 230V, 10A, 1500 rpm DC separately excited motor of 0.2 ohm excited from external DC source of 50 V. Calculate the torque developed by the motor on full load:

1. 13.89 N-m

2. 14.52 N-m

3. 13.37 N-m

4. 14.42 N-m

Show me the answer

Answer: 2) 14.52 N-m

Explanation:

• Back emf $E_b = V - I_a R_a = 230 - 10 \times 0.2 = 228 V$

• Power developed = $E_b \times I_a = 2280 W$

• Torque = $\frac{Power}{\omega} = \frac{2280}{2\pi \times 1500/60} \approx 14.52 N-m$

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76. The candle power of a lamp placed normal to a working plane is 60 CP. Calculate the distance if the illumination is 15 lux:

1. 1.5 m

2. 2.0 m

3. 3.5 m

4. 2.5 m

Show me the answer

Answer: 2) 2.0 m

Explanation:

• Illumination $E = \frac{I}{d^2}$ (for normal incidence)

• $15 = \frac{60}{d^2}$

• $d^2 = 4$

• $d = 2 m$

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77. The percentage reactance of a $100kVA$, $5kV$, $5ohm$ reactance will be:

1. $2\%$

2. $0.2\%$

3. $20\%$

4. $4\%$

Show me the answer

Answer: 3) $20\%$

Explanation:

• %X = $\frac{X \times kVA_{base} \times 10}{kV_{base}^2}$

• = $\frac{5 \times 100 \times 10}{5^2} = \frac{5000}{25} = 200\%$

• Wait, correct formula: %X = $\frac{X \times S_{base}}{V_{base}^2} \times 100\%$

• = $\frac{5 \times 100 \times 10^3}{5000^2} \times 100 = \frac{5 \times 10^5}{25 \times 10^6} \times 100 = 0.02 \times 100 = 2\%$

• So answer is 2% (option 1)

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78. An $800kV$ transmission line has a maximum power transfer capacity of $100MW$. If it is operated at $400kV$ with the series reactance unchanged, then maximum power transfer capacity is approximately:

1. $100MW$

2. $200MW$

3. $25MW$

4. $50MW$

Show me the answer

Answer: 3) $25MW$

Explanation:

• Max power $P_{max} \propto V^2$ for fixed $X$

• At 400kV: $\frac{400^2}{800^2} \times 100 = \frac{1}{4} \times 100 = 25 MW$

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79. Effective monthly interest rate will be ... if nominal interest rate of $10\%$ accounted for continuous compounding:

1. $1\%$

2. $0.84\%$

3. $1.2\%$

4. $2\%$

Show me the answer

Answer: 2) $0.84\%$

Explanation:

• Effective monthly rate $r_m = e^{r/12} - 1 = e^{0.1/12} - 1 \approx 0.00836 \approx 0.836\%$

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80. By considering following activities of a project, the project duration will be:

[Table: A(4), B(5), C(3), D(7), E(5) days, predecessors: A:-, B:-, C:-, D:C, E:A,B,D]

1. 9 days

2. 10 days

3. 15 days

4. 24 days

Show me the answer

Answer: 3) 15 days

Explanation:

Let’s compute it step-by-step using CPM (Critical Path Method).

Given activities

Step 1: Earliest Start (ES) and Earliest Finish (EF)

Activities with no predecessors start at time 0.

• A: ES = 0 → EF = 0 + 4 = 4

• B: ES = 0 → EF = 0 + 5 = 5

• C: ES = 0 → EF = 0 + 3 = 3

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Activity D (depends on C)

• ES = EF of C = 3

• EF = 3 + 7 = 10

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Activity E (depends on A, B, and D)

• ES = max(EF of A, B, D)

• ES = max(4, 5, 10) = 10

• EF = 10 + 5 = 15

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Step 2: Project Duration

The project duration is the maximum EF of the final activities.

Project duration = 15 days.