NBCC Executive Electrical Question Paper Part 5

Q.31 A 400 V 3-phase voltage is applied to a balanced delta connected 3-phase purely resistive load. What is the ratio of reactive power to active power?

1. 0
2. 0.5
3. 1
4. 0.75

Correct Option: 1

Q.32 What happens when gas bubbles collapse in liquid dielectric materials under high electric stress?

1. Heat is generated
2. The bubbles expand
3. Mechanical stress is reduced
4. The dielectric constant decreases

Correct Option: 1

NBCC Executive Electrical Question Paper Part 5

Q.33 What is the primary purpose of a lockout-tagout (LOTO) procedure in electrical safety?

1. To increase the voltage in the electrical system
2. To improve electrical conductivity
3. To isolate and de-energize electrical equipment for maintenance
4. To reduce the need for personal protective equipment

Correct Option: 3

Q.35 What is a notable drawback of using permanent magnet DC generators in some applications?

1. Bulky size
2. High maintenance requirements
3. Limited voltage output
4. Complex control systems

Correct Option: 3

NBCC Executive Electrical Question Paper Part 5

Q.36 What is a key advantage of dielectric heating in food processing applications?

1. It only works for dry food items
2. It preserves food quality by providing slow and gentle heating
3. It relies on conduction to heat food quickly and uniformly
4. It is not suitable for heating food products

Correct Option: 2

Q.37 A magnetic circuit is applied with a current that changes at a rate of 6 A/sec. The circuit has an inductance of 3 H, then the self-induced emf is:

1. -18V
2. 9V
3. 36 V
4. 18V

Correct Option: 1

Q.38 Which safety feature is essential in nuclear power generation to prevent overheating of the reactor core?

1. Control rods
2. Hydroelectric dams
3. Wind turbines
4. Solar panels

Correct Option: 1

NBCC Executive Electrical Question Paper Part 5

Q.39 The armature coils of a 3 phase, 4 pole, 12 slot alternator are short pitched by one slot. Determine the distribution factor and pitch factor.

1. 0.5 and 0.866
2. 1 and 0.866
3. 1 and 1
4. 0.866 and 0.37

Correct Option: 2

Q.40 What is the phenomenon where transmission line conductors can experience significant horizontal motion due to wind-induced vibrations?

1. Tensioning
2. Swinging
3. Galloping
4. Creeping

Correct Option: 3

Q.41 At a certain current,the energy stored in iron cored coil is 500J and its copper loss is 1000W.The time constant (in seconds) of the coil is:

1. 0.25
2. 2.0
3. 1.0
4. 0.5

Correct Option: 3

Q.42 What potential damage can cavitation cause to insulating materials in high-voltage equipment?

1. Improved insulation properties
2. Erosion and material degradation
3. Enhanced heat dissipation
4. Increased dielectric strength

Correct Option: 2

NBCC Executive Electrical Question Paper Part 5

Q.43 In control system analysis, what does the term “loop gain” refer to in the context of an SFG?

1. The product of gains around a closed loop
2. The total gain of a single branch
3. The gain of the forward path
4. The gain of the feedback path

Correct Option: 1

Q.44 A capacitor passes a current of 13.2 mA when supplied with 20 V AC with a frequency of 1 kHz. The capacitance of the capacitor is:

1. 0.1 µF
2. 1 µF
3. 0.1 pF
4. 1 F

Correct Option: 1

Q.45 In a Signal Flow Graph (SFG), what do nodes represent?

1. Summation points
2. Signal destinations
3. Signal sources
4. Gain blocks

Correct Option: 1

NBCC Executive Electrical Question Paper Part 5

Q.46 What happens to the speed of a shunt-wound DC motor as the load torque increases?

1. Speed decreases
2. Speed increases
3. Speed fluctuates
4. Speed remains constant

Correct Option: 1

Q.48 Which type of transmission line structure is commonly used for high-voltage, long-distance transmission lines?

1. Wooden poles
2. Lattice steel towers
3. Concrete poles
4. Underground ducts

Correct Option: 2

NBCC Executive Electrical Question Paper Part 5

Q.49 Infrared radiant heating is often used for heating indoor spaces. Which of the following best describes how it warms objects and surfaces in a room?

1. It relies on convection currents to distribute heat
2. It directly heats the objects and surfaces without significantly warming the air
3. It heats the air, which then warms the objects
4. It operates by blowing hot air into the room

Correct Option: 2

Q.50 As the complexity of a control system increases, how does the number of nodes and branches in the corresponding SFG typically change?

1. Remains constant
2. Decreases
3. Depends on other factors
4. Increases

Correct Option: 4

Q.51 Determine the coupling factor between two coils each having self- inductance of 50 mH and the mutual inductance between them is 50 mH.

1. 0.75
2. 1
3. 2
4. 0.5

Correct Option: 2

NBCC Executive Electrical Question Paper Part 5

Q.53 In an electrical emergency, what should be the first action taken to ensure safety?

1. Increase the electrical load to stabilize the system
2. Disable all safety devices for faster troubleshooting
3. Evacuate the area and call emergency services
4. Attempt to repair the electrical fault immediately

Correct Option: 3

Q.55 Three identical resistors connected in star consume 1000 W when connected across balanced 3-phase supply. What is the power consumed, if the three resistors are connected in delta across the same supply?

1. 9000 W
2. 3000 W
3. 6000 W
4. 1000 W

Correct Option: 2

Q.56 In a star connected 3 phase resistive load, the phase current is 10 A. If the same resistances are connected in delta and same 3 phase Voltage is applied, what is the phase current?

1. 34.64A
2. 12.65A
3. 17.32A
4. 10A

Correct Option: 3

NBCC Executive Electrical Question Paper Part 5

Q.57 Which of the following sentence is NOT suitable for Reproducibility ?

1. It may be specified in terms of units for a given period of time.
2. It refers to the variation in repeat measurements made on the same subject under identical conditions.
3. Perfect reproducibility means that the instrument has no drift.
4. It is the degree of closeness with which a given value may be repeatedly measured.

Correct Option: 2

Q.59 How is the control of reactive power achieved in a synchronous motor?

1. By altering the stator winding configuration
2. By changing the rotor speed
3. By varying the load torque
4. By adjusting the excitation (field) current

Correct Option: 4

NBCC Executive Electrical Question Paper Part 5

Q.60 What term refers to the maximum electric field strength that a dielectric material can withstand without experiencing breakdown?

1. Dielectric constant
2. Dielectric resistance
3. Dielectric capacitance
4. Dielectric strength

Correct Option: 4

NBCC Executive Electrical Question Paper Part 5