BARC Interview Questions and Answers

Q1. Difference between mass and weight
Ans. 
Mass is the amount of matter in an object, while weight is the force exerted on an object due to gravity.
• Mass is a scalar quantity and is measured in kilograms.

• Weight is a vector quantity and is measured in newtons.

• Mass remains constant regardless of the location, while weight varies depending on the gravitational pull.

• Mass can be measured using a balance scale, while weight is measured using a spring scale.

• For example...read more
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Q1. Pass transistor,
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It was a 100 question subject test

Q1. What was your top 3 interested subjects?
Ans. 
My top three favorite subjects are biology, chemistry, and physics, each offering unique insights into the natural world.
• Biology: Fascinated by the complexity of living organisms, I enjoyed studying genetics and ecology, exploring how life interacts with its environment.

• Chemistry: I was captivated by chemical reactions and the periodic table, particularly organic chemistry, which explains the structure and behavior of ...read more
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Q2. In an RLC circuit what is the power quality across inductor
Ans. 
In an RLC circuit, the power quality across an inductor is reactive power.
• The power quality across an inductor in an RLC circuit is reactive power, which means it does not result in actual work being done but rather stores and releases energy in the form of magnetic fields.

• The reactive power in an inductor leads to a phase shift between voltage and current, with the current lagging behind the voltage in an inductive ci...read more
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Q3. Can you use it to transfer active power?
Ans. 
Yes, active power can be transferred using it.
• Yes, active power can be transferred using electrical systems like transformers and transmission lines.

• Active power transfer is essential for the functioning of electrical grids and power distribution networks.

• Examples include transferring power from a power plant to homes and businesses.

• Active power transfer is measured in watts (W) or kilowatts (kW).
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Q4. You mean a lagging zero power factor device can deliver active power?
Ans. 
Yes, a lagging zero power factor device can deliver active power.
• A lagging zero power factor device can still deliver active power because it consumes both real and reactive power.

• The power factor is a measure of how effectively electrical power is being converted into useful work output.

• Even though the power factor may be lagging (less than 1), the device can still deliver active power to the load.

• Examples of devices ...read more
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Q5. When you keep two conductors together with flowing current through them in same direction, what happens to them?
Ans. 
The conductors will attract each other due to the magnetic field produced by the current flowing through them.
• The conductors will experience a force of attraction between them

• This is due to the magnetic field produced by the current flowing through the conductors

• The direction of the current flow will determine the direction of the force
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Q6. What is the basic electrical power equation?
Ans. 
The basic electrical power equation is P = VI, where P is power, V is voltage, and I is current.
• The basic electrical power equation is P = VI

• Power (P) is measured in watts (W)

• Voltage (V) is measured in volts (V)

• Current (I) is measured in amperes (A)

• The equation shows the relationship between power, voltage, and current
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Q7. You mean higher the voltage higher the power
Ans. 
Higher voltage does not necessarily mean higher power, as power is determined by both voltage and current.
• Power is calculated as the product of voltage and current (P = V * I)

• Increasing voltage alone does not always increase power, as current may decrease

• For example, a device operating at 10V and 1A has the same power as a device operating at 5V and 2A
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Q8. Then why do transmission voltage is kept high? Is it not counter intuitive that higher the voltage higher will be the power loss.
Ans. 
Transmission voltage is kept high to reduce power loss over long distances.
• Higher voltage reduces current, which in turn reduces power loss in transmission lines.

• High voltage allows for efficient long-distance transmission without significant power loss.

• Step-up transformers increase voltage for transmission, while step-down transformers decrease voltage for distribution.

• Power loss is proportional to the square of the c...read more
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Q9. What shall be the source impedance for satisfying maximum power transfer in case of AC circuits?
Ans. 
The source impedance for maximum power transfer in AC circuits should be equal to the complex conjugate of the load impedance.
• Source impedance should be equal to the complex conjugate of the load impedance for maximum power transfer.

• This condition ensures that the maximum power is transferred from the source to the load.

• In AC circuits, the source impedance should match the load impedance to achieve maximum power transf...read more
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Q10. Why do you need a complex conjugate to make the power transfer as maximum in simple terms?
Ans. 
Complex conjugate is needed to maximize power transfer by ensuring the impedance matching between the source and load.
• Complex conjugate helps in achieving impedance matching between source and load

• Impedance matching minimizes reflections and maximizes power transfer

• By taking the complex conjugate, the real part of the impedance is matched while the imaginary part cancels out
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Q11. Why common emitter is also called as inverter?
Ans. 
Common emitter is called an inverter because it produces an output that is the opposite of the input signal.
• In a common emitter configuration, the output signal is 180 degrees out of phase with the input signal.

• The common emitter amplifier produces a phase shift of 180 degrees, effectively inverting the input signal.

• This inversion property is why the common emitter amplifier is also known as an inverter.
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Q12. Which configuration of transistor is called as buffer and why?
Ans. 
A transistor configuration with high input impedance and low output impedance is called a buffer.
• Buffers are used to isolate two circuits with different impedance levels.

• Common emitter or common collector configurations are often used as buffers.

• Buffers help prevent loading effects and signal distortion in electronic circuits.
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Q13. Can an opAmp be used as a computer?
Ans. 
No, an opAmp cannot be used as a computer.
• OpAmps are analog devices used for amplifying signals, not for digital computation.

• OpAmps lack the necessary components such as memory, processing units, and input/output interfaces to function as a computer.

• Computers require complex digital circuits and software to perform tasks, which opAmps are not designed for.
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Q14. Can you draw the two transistor model of a Silicon Controlled Rectifier and explain how it gets forward conductive with gate pulse?
Ans. 
The two transistor model of a Silicon Controlled Rectifier consists of an NPN and PNP transistor connected in a feedback loop.
• The NPN transistor is connected in series with the PNP transistor, forming a regenerative feedback loop.

• When a gate pulse is applied, it triggers the NPN transistor to turn on, which in turn triggers the PNP transistor to turn on.

• This regenerative process continues until the SCR is in forward co...read more
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Q15. Why single phase induction is not self starting by nature?
Ans. 
Single phase induction motors are not self-starting due to the absence of a rotating magnetic field.
• Single phase induction motors lack a rotating magnetic field, which is necessary for self-starting.

• The starting torque in single phase motors is zero, making it impossible for them to start on their own.

• Additional starting mechanisms such as capacitors or shaded poles are required to create the necessary rotating magneti...read more
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Q16. Why DC series motor is preferred for traction applications
Ans. 
DC series motor is preferred for traction applications due to its high starting torque and speed control capabilities.
• DC series motor provides high starting torque, making it suitable for traction applications where high torque is required to start moving heavy loads.

• DC series motor offers good speed control capabilities, allowing for smooth acceleration and deceleration in traction applications.

• DC series motor is simp...read more
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Q17. What are the limitations of KCL and KVL
Ans. 
KCL and KVL have limitations in complex circuits and non-linear components.
• KCL assumes all currents entering a node must equal all currents leaving, which may not hold true in complex circuits.

• KVL assumes the sum of voltage drops in a closed loop is zero, which may not be accurate in circuits with non-linear components.

• Both laws are based on ideal conditions and may not be applicable in real-world scenarios.

• KCL and KVL...read more
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Q18. Where do you use Barkhausen Criteria
Ans. 
Barkhausen Criteria is used in determining the conditions for the onset of magnetic domain wall motion in ferromagnetic materials.
• Used in understanding the behavior of magnetic domains in ferromagnetic materials

• Helps in predicting the conditions for the initiation of magnetic domain wall motion

• Important in the study of magnetic hysteresis and magnetic materials
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Q19. Why 25 KV is preferred for railway traction?
Ans. 
25 KV is preferred for railway traction due to its higher efficiency, reduced power loss, and ability to support longer distances.
• 25 KV allows for higher speeds and heavier loads compared to lower voltages like 1.5 KV or 3 KV

• It reduces power loss during transmission, leading to higher efficiency and cost savings

• Higher voltage enables longer distances between substations, reducing infrastructure costs

• 25 KV is a standard...read more
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Q1. Explain what is rotating magnetic field in an ac motor
Ans. 
Rotating magnetic field in an AC motor is a magnetic field that rotates within the motor, causing the rotor to turn and generate mechanical energy.
• Rotating magnetic field is created by the interaction of stator windings with the alternating current flowing through them.

• The rotating magnetic field induces currents in the rotor, which in turn creates a torque that causes the rotor to rotate.

• This rotation of the rotor is ...read more
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Q2. Nyqyuist plot of typical systems
Ans. 
Nyquist plot is a graphical representation of a system's frequency response in the complex plane.
• Nyquist plot shows how a system responds to sinusoidal inputs at different frequencies.

• It is used to analyze stability and performance of control systems.

• The plot typically consists of a plot of the real part of the transfer function against the imaginary part.

• Nyquist plots are commonly used in control engineering and signa...read more
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Q3. What happens to performance of a transformer if we remove a slice of the core
Ans. 
Removing a slice of the core in a transformer can lead to decreased efficiency and increased losses.
• Removing a slice of the core can disrupt the magnetic flux path, leading to increased eddy current losses.

• It can also result in increased hysteresis losses, as the magnetic field is no longer evenly distributed.

• Overall, the performance of the transformer will be negatively impacted, with decreased efficiency and potentia...read more
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Q4. Explain the working principle of induction motor
Ans. 
An induction motor works on the principle of electromagnetic induction to generate rotating magnetic field.
• Induction motor has a stator with a set of windings that are connected to an AC power supply.

• When AC current flows through the stator windings, it produces a rotating magnetic field.

• This rotating magnetic field induces current in the rotor windings, causing it to rotate.

• The rotor never reaches the synchronous spee...read more
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Q5. What happens to voltage of the transformer if remove crosssectional slice of the core
Ans. 
Removing a cross-sectional slice of the core in a transformer will decrease the voltage.
• Removing a cross-sectional slice of the core reduces the magnetic flux in the transformer

• This reduction in magnetic flux leads to a decrease in the induced voltage in the windings

• As a result, the voltage output of the transformer decreases

• This can impact the efficiency and performance of the transformer
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Q1. On corona discharge.
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Q1. They ask mostly related about internships, fieldwork, academic basics
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