30+ BARC Interview Questions and Answers for Freshers

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

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 potentially increased heating.

• For example, if a slice of the core ...read more

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 what drives the mechanical output of the AC motor.

• The spee...read more

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 speed of the rotating magnetic field, resulting in continuous ...read more

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 signal processing.

• Example: Nyquist plot of a stable system will...read more

Answers to questions related to electrical machines and motors.

• Hysteresis loss is the energy lost due to the reversal of magnetic field in a ferromagnetic material.

• Eddy current loss is the energy lost due to the flow of eddy currents in a conductor.

• Cylindrical and salient pole machines use sinusoidal current to produce a rotating magnetic field.

• Ceiling fans use induction motors which work on the principle of rotating magnetic field.

• A capacitor is not necessary to start a ceil...read more

The output voltage of a mobile charger is 3.5V. Calculate the rating of the transformer used.

• The transformer rating depends on the input voltage and current, not the output voltage.

• The output voltage is regulated by the charger circuitry.

• The transformer rating can be calculated using the formula: Power = Voltage x Current.

• Without knowing the input voltage and current, the transformer rating cannot be calculated.

Answering how 3-phase magnetic field is produced and its constant magnitude.

• Three-phase magnetic field is produced by three alternating currents with a phase difference of 120 degrees.

• The magnitude of the magnetic field is constant because the three currents are balanced and symmetrical.

• This results in a rotating magnetic field that is used in many applications such as electric motors.

• The magnitude of the magnetic field can be calculated using the formula B = (4π/√3) * (N/L) ...read more

Generator and motor experience voltage fluctuations during Ferranti effect, while transmission line experiences voltage rise.

• Ferranti effect is a phenomenon of voltage rise at the receiving end of a long transmission line due to capacitance between the line and ground

• Generators and motors experience voltage fluctuations due to the voltage rise at the receiving end

• This can cause damage to the insulation of the machines and affect their performance

• Transmission line experiences ...read more

Harmonics can be reduced by using various winding techniques such as delta, wye, zigzag, etc.

• Use delta winding for three-phase motors

• Use wye winding for single-phase motors

• Zigzag winding can be used for transformers

• Use multiple winding layers to reduce harmonics

• Use low resistance wire to reduce skin effect

• Use magnetic shielding to reduce electromagnetic interference

• Use active filters or passive filters to reduce harmonics in power systems

DC machines can be classified into two types: DC motors and DC generators. The speed-torque characteristic of DC machines varies based on their type and construction.

• DC motors can be classified into shunt, series, and compound motors

• DC generators can be classified into separately excited, shunt, series, and compound generators

• Shunt motors have a nearly constant speed-torque characteristic

• Series motors have a high starting torque and variable speed-torque characteristic

• Compoun...read more

Armature reaction is the effect of magnetic field produced by armature current on the main magnetic field. Interpole winding is used to counteract this effect.

• Armature reaction is the distortion of the main magnetic field due to the magnetic field produced by the armature current.

• Interpole winding is a small winding placed in the pole faces of DC machines to counteract the effect of armature reaction.

• Interpole winding produces a magnetic field that opposes the armature reacti...read more

Torque is produced in synchronous machines due to the interaction between the magnetic fields of the stator and rotor.

• The stator magnetic field induces a current in the rotor winding, creating a magnetic field in the rotor.

• The interaction between the stator and rotor magnetic fields produces a torque that drives the rotor.

• The amount of torque produced depends on the strength of the magnetic fields and the angle between them.

• Synchronous machines are commonly used in power gene...read more

Certain conditions must be met for production of torque in any machine.

• Presence of a magnetic field

• Flow of current through the conductor

• Interaction between the magnetic field and the current

• The angle between the magnetic field and the current

• The number of turns in the conductor

• The strength of the magnetic field

• The amount of current flowing through the conductor

• The length of the conductor

• The presence of a commutator or slip rings

• Examples: electric motors, generators, transform...read more

Torque is produced in DC, synchronous, and induction machines through the interaction of magnetic fields.

• DC machines use commutators to switch the direction of current flow in the armature, creating a magnetic field that interacts with the field produced by the stator.

• Synchronous machines use a magnetic field produced by a DC current in the rotor to interact with the stator's magnetic field.

• Induction machines use the interaction between the rotating magnetic field produced by...read more

Inductors, capacitors, and resistors can be designed using VLSI technology.

• Inductors can be designed using spiral inductors or solenoid inductors.

• Capacitors can be designed using metal-insulator-metal (MIM) capacitors or varactor diodes.

• Resistors can be designed using thin-film resistors or polysilicon resistors.

• VLSI technology allows for the integration of these components onto a single chip.

• The design process involves selecting the appropriate materials and dimensions for e...read more

Noise in CDMA signals is shown by measuring the signal-to-noise ratio (SNR).

• Noise in CDMA signals is typically measured by the signal-to-noise ratio (SNR).

• The type of noise in CDMA signals can vary, but common types include thermal noise and interference from other signals.

• To improve SNR and reduce noise, CDMA systems use techniques such as power control and interference cancellation.

• Noise in CDMA signals can also be caused by environmental factors such as weather and terrain...read more

An inverter circuit diagram can be drawn using a NOT gate. A clock can be made using a crystal oscillator and a counter.

• Inverter circuit diagram can be drawn using a NOT gate

• A clock can be made using a crystal oscillator and a counter

• Clock arrangement can be made using a 555 timer IC

• Inverter circuit can be used to convert DC to AC

Inductor is a passive component that stores energy in a magnetic field. It is used in VLSI for filtering and signal processing.

• Inductor is used in VLSI for filtering and signal processing.

• It stores energy in a magnetic field.

• It is a passive component.

• Inductors are commonly used in RF circuits.

• Inductors can be modeled as a series of inductances and resistances.

• Inductors can be used to create resonant circuits.

Armature reaction helps in improving the commutation process in DC machines.

• Reduces sparking at the brushes

• Improves the efficiency of the machine

• Helps in maintaining a constant voltage output

• Enables the machine to handle heavy loads

• Reduces the wear and tear of the brushes

• Prevents the demagnetization of the field winding

SCR stands for Silicon Controlled Rectifier. We use overvoltage and overcurrent protection for SCR.

• SCR is a type of semiconductor device used for power control and switching.

• It is commonly used in electronic circuits for controlling high power devices such as motors, heaters, and lamps.

• Overvoltage protection is used to prevent damage to the SCR due to excessive voltage, while overcurrent protection is used to prevent damage due to excessive current.

• Examples of protection devi...read more

Frequency and voltage can be controlled through various methods such as transformers, generators, and voltage regulators.

• Transformers can be used to step up or step down voltage levels

• Generators can be used to produce a specific frequency and voltage

• Voltage regulators can be used to maintain a constant voltage level

• Frequency converters can be used to change the frequency of an AC power source

• Power inverters can be used to convert DC voltage to AC voltage

To generate a given waveform using an asynchronous counter, follow these steps:

• Determine the number of flip-flops required based on the waveform's frequency

• Design the counter circuit using JK flip-flops

• Connect the output of the counter to a digital-to-analog converter (DAC)

• Feed the DAC output to a low-pass filter to obtain the waveform

• Adjust the counter's clock frequency to match the desired waveform frequency

Signal can be transferred from one mobile to another via Bluetooth, Wi-Fi Direct, or mobile data.

• Enable Bluetooth or Wi-Fi Direct on both devices and pair them to transfer files.

• Use mobile data to transfer files via cloud storage or file-sharing apps.

• NFC can also be used for transferring small files.

• Third-party apps like SHAREit, Xender, and AirDroid can also be used for file transfer.

• Signal can also be transferred via cable using USB OTG.

Two field revolving theory is a concept in physics that explains the behavior of charged particles in a magnetic field.

• The theory states that a charged particle moving in a magnetic field experiences a force perpendicular to both the magnetic field and the direction of motion.

• This force causes the particle to move in a circular path, with the radius of the circle determined by the particle's speed and the strength of the magnetic field.

• The theory is used to explain phenomena ...read more

Yes, we use transformers in our homes.

• Transformers are used to step up or step down the voltage of electricity in our homes.

• Step-down transformers are used to reduce the voltage from the power grid to a safe level for household use.

• Step-up transformers are used to increase the voltage for transmission over long distances.

• Transformers are also used in electronic devices like chargers and power adapters.

• Without transformers, we would not be able to use electricity safely and ef...read more

Slip and speed characteristic of Induction M/c is an important aspect of its performance.

• Slip is the difference between synchronous speed and rotor speed.

• Speed characteristic curve shows the relationship between speed and torque.

• At synchronous speed, slip is zero and torque is maximum.

• As slip increases, torque decreases.

• At maximum slip, torque is zero.

• Speed characteristic curve is used to determine the operating point of the motor.

• Induction motors have high starting torque an...read more

Synchronous counters use clock signals to change state, while asynchronous counters use external inputs.

• Synchronous counters use flip-flops that change state on the rising or falling edge of a clock signal.

• Asynchronous counters use flip-flops that change state based on external inputs, such as a button press or sensor reading.

• Synchronous counters are more reliable and accurate, but require a clock signal.

• Asynchronous counters are simpler and more flexible, but can be less rel...read more

Transformers are used to transfer electrical energy from one circuit to another through electromagnetic induction.

• Transformers are used in power distribution systems to step up or step down voltage levels.

• They are used in electronic devices to isolate circuits and match impedance.

• Transformers are also used in welding machines, audio equipment, and medical equipment.

• They are essential in the transmission and distribution of electricity over long distances.

• Transformers are used...read more

Induction machines work on the principle of electromagnetic induction to convert electrical energy into mechanical energy.

• Induction machines have a stator and a rotor

• The stator has a set of coils that are supplied with AC current

• This creates a rotating magnetic field that induces a current in the rotor

• The rotor current interacts with the magnetic field to produce torque and rotation

• Induction machines are commonly used in industrial applications such as pumps, fans, and compre...read more

Ferranti effect is the voltage rise at the receiving end of a long transmission line when the line is lightly loaded.

• Occurs in long transmission lines with low power demand

• Voltage at the receiving end is higher than the sending end

• Caused by the capacitance of the line

• Can be compensated by adding inductance to the line

• Can cause overvoltage and damage to equipment

CDMA stands for Code Division Multiple Access. It is a wireless communication technology that allows multiple users to share the same frequency band simultaneously.

• CDMA uses unique codes to differentiate between users and their transmissions.

• It allows for more efficient use of available bandwidth.

• CDMA is used in cellular networks, such as Verizon and Sprint in the US.

• It is also used in other wireless communication systems, such as satellite and Wi-Fi.

• CDMA is known for its hig...read more

Power angle is important in power system stability analysis and control.

• Power angle is the phase difference between voltage and current in an AC power system.

• It affects the power flow and stability of the system.

• A large power angle can cause instability and blackouts.

• Power angle is controlled by adjusting the generator output and transmission line parameters.

• Power angle is used in the calculation of power transfer limits and voltage stability margins.