30+ Interview Questions and Answers

The Hagen-Poiseuille equation describes the flow of a viscous fluid through a cylindrical pipe or tube.

• The equation relates the flow rate of the fluid to the pressure difference, viscosity, length, and radius of the pipe.

• It can be used to calculate the flow rate or pressure drop in various fluid systems, such as blood flow in blood vessels or water flow in pipes.

• The equation assumes laminar flow, where the fluid flows smoothly in parallel layers without turbulence.

• It is often...read more

A daily used CSTR type equipment in kitchen is a pressure cooker.

• Pressure cookers are used to cook food quickly and efficiently.

• They work by trapping steam inside the pot, which raises the pressure and temperature.

• This allows food to cook faster and retain more nutrients.

• Examples of dishes that can be made in a pressure cooker include soups, stews, and rice.

• Pressure cookers come in different sizes and materials, such as stainless steel and aluminum.

Bernoulli's equation relates the pressure, velocity, and height of a fluid in motion.

• The equation is based on the conservation of energy principle.

• It is commonly used in fluid mechanics to analyze the flow of fluids through pipes and over surfaces.

• The equation assumes that the fluid is incompressible, non-viscous, and steady-state.

• It also assumes that the flow is laminar and that there is no heat transfer or work done on the fluid.

• Limitations include its inability to accurate...read more

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

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 conductive state.

• The gate pulse must be of sufficient amplit...read more

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 current, so reducing current by increasing voltage helps mi...read more

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 transfer.

• The formula for maximum power transfer is Zs = Zl* wher...read more

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

Heat exchangers are devices used to transfer heat between two or more fluids.

• Types of heat exchangers include shell and tube, plate, and finned tube heat exchangers.

• Selection criteria for heat exchangers include heat transfer efficiency, pressure drop, material compatibility, and cost.

• Shell and tube heat exchangers are commonly used in industries such as oil and gas, chemical, and power generation.

• Plate heat exchangers are compact and efficient, suitable for applications with...read more

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 circuit.

• The power factor in an inductive circuit is less tha...read more

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.

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 magnetic field for starting.

• Once the motor reaches a certain spee...read more

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

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 simple in design and easy to maintain, making it cost-effectiv...read more

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 with lagging zero power factor include induction motors an...read more

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

Velocity profiles inside pipeline and boundary layer formations

• Velocity profiles inside a pipeline refer to the distribution of fluid velocities across the cross-section of the pipe.

• Boundary layer formations occur when fluid flows over a solid surface, creating a thin layer of fluid near the surface with different velocity characteristics.

• Velocity profiles inside a pipeline can be influenced by factors such as pipe diameter, flow rate, and fluid viscosity.

• Boundary layer forma...read more

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

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.

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 voltage used in many countries for railway electrificatio...read more

Valves are used to control fluid flow. Different types include gate, globe, ball, butterfly, and needle valves.

• Gate valves: used for full open or full close control

• Globe valves: used for throttling control

• Ball valves: used for quick shut-off control

• Butterfly valves: used for low-pressure control

• Needle valves: used for precise flow control

• Other types include diaphragm, pinch, and check valves

In a co-current heat exchanger, the hot and cold fluids flow in the same direction, resulting in a gradual decrease in temperature. In a counter current heat exchanger, the fluids flow in opposite directions, leading to a more efficient heat transfer.

• Co-current heat exchanger: gradual decrease in temperature

• Counter current heat exchanger: more efficient heat transfer

• Co-current: hot and cold fluids flow in the same direction

• Counter current: hot and cold fluids flow in opposite...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

Pump characteristic curves show the relationship between flow rate, head, and power.

• Pump characteristic curves depict the performance of a pump under different operating conditions.

• The curves show the relationship between flow rate (Q), head (H), and power (P).

• The curves help in selecting the right pump for a specific application.

• The curves can be used to determine the efficiency and operating range of a pump.

• Different types of pumps have different characteristic curves.

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).

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.

The McCabe Thiele method is a graphical technique used to analyze binary distillation processes.

• Assumes constant molar overflow

• Assumes constant relative volatility

• Assumes ideal behavior of the components

• Assumes equilibrium between liquid and vapor phases

• Assumes constant molar flow rates

• Assumes constant temperature and pressure

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 do not account for parasitic elements like capacitance an...read more

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

A design methodology for a heat exchanger involves several steps and considerations.

• Identify the heat transfer requirements and constraints

• Determine the type and size of heat exchanger suitable for the application

• Select the appropriate materials for construction

• Calculate the required surface area for heat transfer

• Design the flow arrangement and determine the fluid flow rates

• Consider pressure drop and fouling factors

• Perform thermal and mechanical design calculations

• Optimize th...read more

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

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

The various phases in heating liquid are solid, liquid, and gas.

• Heating a solid substance causes it to melt and become a liquid.

• Continued heating of the liquid causes it to evaporate and become a gas.

• Examples include heating ice to form water and then heating water to form steam.