Q1. Electric supply system mainly consists of:
A) Generation only
B) Generation and transmission
C) Generation, transmission and distribution
D) Transmission and utilization
Correct Option: C
Explanation: An electric supply system includes generation of power, transmission at high voltage, and distribution to consumers at utilization voltage.
Q2. The most economical system for bulk power supply is:
A) D.C. supply system
B) Single-phase A.C. system
C) Three-phase A.C. system
D) Single-wire earth return system
Correct Option: C
Explanation: Three-phase A.C. system transmits more power with less conductor material and lower losses.
Q3. A typical A.C. power supply scheme uses transmission at:
A) Low voltage, high current
B) High voltage, low current
C) Low voltage, low current
D) High voltage, high current
Correct Option: B
Explanation: High voltage reduces current and hence minimizes I²R losses.
Q4. Which factor mainly decides transmission voltage selection?
A) Power factor
B) Insulation cost
C) Line losses
D) All of the above
Correct Option: D
Explanation: Transmission voltage depends on losses, insulation cost, power factor, mechanical strength, and safety.
Q5. One major disadvantage of D.C. transmission is:
A) High corona loss
B) Difficulty in voltage transformation
C) Poor efficiency
D) High reactive power
Correct Option: B
Explanation: D.C. voltage cannot be stepped up or down easily without costly converters.
Q6. Compared to A.C. transmission, D.C. transmission has:
A) Higher line losses
B) Lower efficiency
C) No skin effect
D) Higher corona loss
Correct Option: C
Explanation: In D.C. transmission, current is uniformly distributed, so skin effect does not occur.
Q7. Advantage of high transmission voltage is:
A) Reduced conductor size
B) Reduced I²R loss
C) Improved voltage regulation
D) All of the above
Correct Option: D
Explanation: High voltage reduces current, lowering losses, conductor size, and improving regulation.
Q8. For long distance bulk power transmission, preferred system is:
A) D.C. overhead
B) Single-phase A.C.
C) Three-phase A.C.
D) Underground A.C.
Correct Option: C
Explanation: Three-phase A.C. allows easy voltage transformation and high efficiency.
Q9. Site selection for a nuclear power station mainly depends on:
A) Coal availability
B) Water availability
C) Nearness to load center
D) Transportation only
Correct Option: B
Explanation: Nuclear plants require large quantities of water for cooling and condenser operation.
Q10. Nuclear power stations are preferably located:
A) In cities
B) Near coal mines
C) Away from populated areas
D) Near load center
Correct Option: C
Explanation: Safety and radiation concerns require nuclear plants to be away from populated regions.
Q11. Transmission voltage is doubled. Power transmitted remains same. Line current will:
A) Double
B) Become half
C) Remain same
D) Become four times
Correct Option: B
Explanation: Since P = VI, doubling voltage halves the current.
Q12. If transmission voltage is increased by 4 times, copper loss becomes:
A) Same
B) 1/2
C) 1/4
D) 1/16
Correct Option: D
Explanation: Loss ∝ I² and I ∝ 1/V, so loss reduces by (1/4)² = 1/16.
Q13. A 3-phase line transmits same power at 66 kV and later at 132 kV. Ratio of losses is:
A) 1:1
B) 1:2
C) 1:4
D) 4:1
Correct Option: D
Explanation: Doubling voltage halves current; losses reduce by factor of 4.
Q14. Power transmitted = 100 MW, line voltage = 100 kV, efficiency = 90%. Find line current.
A) 577 A
B) 641 A
C) 1111 A
D) 1000 A
Correct Option: B
Explanation: I = P / (√3 × V × η) ≈ 641 A.
Q15. Transmission voltage increased from 50 kV to 100 kV. Percentage reduction in I²R loss is:
A) 25%
B) 50%
C) 75%
D) 100%
Correct Option: C
Explanation: Loss reduces to one-fourth, hence 75% reduction.
Q16. For constant power, transmission loss is proportional to:
A) V
B) 1/V
C) 1/V²
D) V²
Correct Option: C
Explanation: Loss ∝ I² and I ∝ 1/V, hence loss ∝ 1/V².
Q17. Power transmitted = 10 MW at 10 kV. Find current.
A) 100 A
B) 500 A
C) 1000 A
D) 2000 A
Correct Option: C
Explanation: I = P/V = (10×10⁶)/(10×10³) = 1000 A.
Q18. Gas turbine power plant is preferred for:
A) Base load
B) Peak load
C) Continuous load
D) Nuclear backup
Correct Option: B
Explanation: Gas turbine plants have quick starting and fast load response.
Q19. Major advantage of gas turbine power plant is:
A) High efficiency
B) Low capital cost
C) Long starting time
D) High fuel consumption
Correct Option: B
Explanation: Gas turbine plants have compact size and low initial cost.
Q20. Which power plant has the least starting time?
A) Steam
B) Nuclear
C) Gas turbine
D) Hydro
Correct Option: C
Explanation: Gas turbine plants can start within minutes, making them the fastest.