NTPC PREVIOUS QUESTIONS:
NTPC PREVIOUS QUESTIONS -1 with multiple choices, along with answers provided after each question:
1. In an electrical circuit, the unit of power is:
a) Volt
b) Watt
c) Ampere
d) Ohm
Answer: b) Watt
2. The unit of capacitance is:
a) Ohm
b) Farad
c) Tesla
d) Watt
Answer: b) Farad
3. What is the purpose of a transformer?
a) To increase current
b) To increase voltage
c) To decrease current
d) To decrease voltage
Answer: b) To increase voltage
4. The material used for making the armature of a DC motor is generally:
a) Copper
b) Aluminium
c) Steel
d) Iron
Answer: d) Iron
5. In a three-phase system, the total power is given by:
a) P = V * I * √3
b) P = V * I * 2
c) P = V * I * 3
d) P = V * I
Answer: a) P = V * I * √3
6. The efficiency of a transformer is highest at:
a) Full load
b) Half load
c) No load
d) Any load
Answer: a) Full load
7. The speed of a three-phase induction motor depends on:
a) Supply frequency
b) Supply voltage
c) Both a and b
d) None of the above
Answer: a) Supply frequency
8. Which of the following is a non-renewable energy source?
a) Wind energy
b) Solar energy
c) Coal
d) Geothermal energy
Answer: c) Coal
9. What is the primary function of an alternator in a power plant?
a) To convert chemical energy into mechanical energy
b) To convert mechanical energy into electrical energy
c) To regulate voltage
d) To store electrical energy
Answer: b) To convert mechanical energy into electrical energy
10. The voltage rating of a battery is measured in:
a) Amperes
b) Watts
c) Volts
d) Coulombs
Answer: c) Volts
11. What is the effect of adding resistance to a series circuit?
a) Current increases
b) Current decreases
c) Voltage decreases
d) Power decreases
Answer: b) Current decreases
12. The energy consumed in an electrical circuit is measured in:
a) Joules
b) Watts
c) Amperes
d) Ohms
Answer: a) Joules
13. What is the main advantage of high voltage transmission?
a) Reduced losses
b) Increased current
c) Decreased resistance
d) Decreased power factor
Answer: a) Reduced losses
14. The earth wire is used in electrical circuits to:
a) Increase current flow
b) Protect against electric shock
c) Increase voltage
d) Stabilize frequency
Answer: b) Protect against electric shock
15. In a series circuit, the total resistance is:
a) The sum of individual resistances
b) The difference of individual resistances
c) The reciprocal of individual resistances
d) Equal to the highest resistance
Answer: a) The sum of individual resistances
16. Which device is used to measure the current in a circuit?
a) Voltmeter
b) Ammeter
c) Ohmmeter
d) Galvanometer
Answer: b) Ammeter
17. A DC motor can be controlled by adjusting:
a) Voltage
b) Current
c) Both voltage and current
d) Resistance only
Answer: c) Both voltage and current
18. The efficiency of an electric motor is defined as:
a) Output power / Input power
b) Input power / Output power
c) Output power x Input power
d) Output power + Input power
Answer: a) Output power / Input power
19. Which of the following materials is best suited for making the core of a transformer?
a) Copper
b) Silicon steel
c) Aluminium
d) Cast iron
Answer: b) Silicon steel
20. A 3-phase induction motor operates on the principle of:
a) Electromagnetic induction
b) Magnetic attraction
c) Electric repulsion
d) Electrolysis
Answer: a) Electromagnetic induction
21. The function of a capacitor in an AC circuit is to:
a) Store electrical energy
b) Regulate voltage
c) Increase current flow
d) Convert AC to DC
Answer: a) Store electrical energy
22. In an induction motor, the rotor is:
a) Permanently magnetized
b) Energized by an external source
c) Induced with current by the stator field
d) Used to generate the electric field
Answer: c) Induced with current by the stator field
23. A material with high resistivity is used in:
a) Conductors
b) Insulators
c) Semi-conductors
d) Superconductors
Answer: b) Insulators
24. Which of the following is a correct statement regarding transformers?
a) The primary coil is always at high voltage
b) The secondary coil always carries the same voltage
c) The ratio of primary to secondary voltage is the same as the ratio of current
d) The primary and secondary coils are electrically connected
Answer: c) The ratio of primary to secondary voltage is the same as the ratio of current
25. The power factor of an ideal circuit is:
a) 1
b) 0
c) ∞
d) 0.5
Answer: a) 1
26. In a synchronous motor, the rotor speed is:
a) Always less than the synchronous speed
b) Always equal to the synchronous speed
c) Always greater than the synchronous speed
d) None of the above
Answer: b) Always equal to the synchronous speed
27. The purpose of an earth leakage circuit breaker (ELCB) is to:
a) Break the circuit in case of overload
b) Protect the circuit from short circuits
c) Detect leakage current and protect against electric shocks
d) Prevent the circuit from being overloaded
Answer: c) Detect leakage current and protect against electric shocks
28. The SI unit of electric current is:
a) Volt
b) Watt
c) Ampere
d) Coulomb
Answer: c) Ampere
29. Which of the following is the main advantage of a high-efficiency electric motor?
a) Increased power consumption
b) Increased load handling capacity
c) Reduced energy consumption
d) Reduced size
Answer: c) Reduced energy consumption
30. What is the effect of frequency on the inductive reactance of an AC circuit?
a) It decreases with frequency increase
b) It increases with frequency increase
c) It remains constant with frequency
d) It is inversely proportional to frequency
Answer: b) It increases with frequency increase
31. A moving coil galvanometer can be converted into an ammeter by:
a) Connecting a low resistance in series
b) Connecting a high resistance in series
c) Connecting a low resistance in parallel
d) Connecting a high resistance in parallel
Answer: a) Connecting a low resistance in series
32. The current in a capacitor in an AC circuit is:
a) In phase with the voltage
b) Leading the voltage by 90°
c) Lagging the voltage by 90°
d) Out of phase with the voltage
Answer: b) Leading the voltage by 90°
33. The function of a fuse is to:
a) Protect the circuit from overload
b) Convert AC to DC
c) Regulate voltage
d) Increase the current
Answer: a) Protect the circuit from overload
34. A transformer works on the principle of:
a) Magnetic induction
b) Electrostatic induction
c) Faraday’s law of electromagnetic induction
d) Coulomb’s law
Answer: c) Faraday’s law of electromagnetic induction
35. A 3-phase alternator produces an EMF with a phase difference of:
a) 0°
b) 60°
c) 90°
d) 120°
Answer: d) 120°
36. The power loss in a transmission line is mainly due to:
a) Capacitive reactance
b) Inductive reactance
c) Resistive heating
d) Magnetic flux leakage
Answer: c) Resistive heating
37. In an electric motor, the mechanical power output is given by:
a) P = I²R
b) P = VI
c) P = V²/R
d) P = Torque x Speed
Answer: d) P = Torque x Speed
38. In a series LCR circuit, resonance occurs when:
a) Inductive reactance is equal to capacitive reactance
b) Inductive reactance is greater than capacitive reactance
c) Capacitive reactance is greater than inductive reactance
d) Total impedance is zero
Answer: a) Inductive reactance is equal to capacitive reactance
39. The maximum efficiency of an electrical motor occurs when:
a) The copper losses equal the iron losses
b) The iron losses equal the mechanical losses
c) The copper losses are greater than the iron losses
d) The mechanical losses are greater than the iron losses
Answer: a) The copper losses equal the iron losses
40. In a power system, the purpose of a circuit breaker is to:
a) Provide continuous power supply
b) Interrupt current flow during fault conditions
c) Increase the voltage in a circuit
d) Convert DC to AC
Answer: b) Interrupt current flow during fault conditions
These questions cover various electrical engineering topics, including power systems, electrical machines, and circuit theory.
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