Electrical Safety

Electrical Safety Rules- When performing electrical work, it is critical to ensure that there is no electrical shock. Today I will discuss electrical hazards and precautions in relation to the issue of electrical safety. Be aware of it and take precautions so that no electrical accidents occur in the future.

What is Electricity? - Electricity is a tremendously useful, clean, and convenient energy source. However, if we do not handle it appropriately, it can become extremely harmful and endanger our lives.

Common Hazards In Electrical Job

• Electric Shock
• Electric  Fire and Burns
• Electric Arc Flash/blast

Body Resistance Value of Human 

On dry skin → 10000 to 60,000 Ohms

On wet skin → 1000 Ohms

Hand to foot → 400 to 600 Ohms

Safe Work Procedure - During electrical work always insure that the incomer supply is in off condition and for this switch off the incomer MCB in General work like work at home etc.

When you work in the industry always work on the machines after taken the Lock on the incoming feeder,this procedure is called LOTOTO System in industry.

Electrical Safety Rules - Always take care and follow the below mention rules when work on electricity.

• wearing hand gloves

• put on a safety helmet

• wear a safety belt when work at height 

• wear insulated shoes

• use insulated tools

Electrical Hazards

• Burns and electric shock from coming into contact with live parts
• Harm caused by arcing, which occurs when electricity leaps from one circuit to another.
• Fire caused by improper electrical connections or equipment
• Explosion brought on by improper electrical equipment
• Combustible dusts or vapors’ being  ignited by static

Vacuum Circuit Breaker

Circuit breakers are mechanical devices that are meant to close or open an electrical circuit under normal and abnormal conditions.

What exactly is VCB?

VCB stands for vacuum circuit breaker and is a type of switchgear used for voltages greater than 1 or 3.3 KV. In vacuum circuit breakers, the vacuum used as the arc quenching medium. The vacuum has the greatest insulating strength. 

High interruption capability, longer operation life, safety, and high cost-performance are all properties of VCB.

When the contacts of a breaker are opened in a vacuum, for example, the interruption happens at initial current zero, with dielectric strength between the contacts increasing at a pace thousands of times faster than with other types of circuit breakers.

Working Principle

According to the vacuum circuit breaker operating theory, when the contacts of the circuit breaker are opened in a vacuum, an arc can be produced between the contacts due to the ionization of metal vapors in the contacts. However, the arc is swiftly extinguished because the metallic vapors, electrons, and ions that are produced throughout the arc quickly condense over the outsides of the CB contacts, allowing the dielectric strength to be quickly restored.

The most crucial characteristic of a vacuum is that, once an arc has been created there, it may be swiftly put out due to the vacuum's fast increase in dielectric strength.

Construction of vacuum circuit breaker-

A steel arc chamber is part of the center-symmetrically organized ceramic insulators' vacuum circuit breaker a steel arc chamber is part of the center-symmetrically organized ceramic insulators' vacuum circuit breaker.

The vacuum circuit breaker performance is significantly influenced by the material selected for the current-carrying contacts. Copper-bismuth or copper-chrome alloys are the best materials to use when creating VCB connections.

A moving contact, a fixed contact, and a vacuum interrupter make up the vacuum circuit breaker. A stainless steel bellow connects the moving contact to the control mechanism. The insulating housing supports the arc shields in such a way that they cover the shields and prevent condensation on the enclosure from occurring.

Below image, you can see all the important parts of the VCB.

Vacuum Interrupter

The interruption of arc in a Vacuum Circuit Breaker is carried out by the vacuum interrupters.

A vacuum interrupter, in theory, contains ceramic insulators stacked symmetrically and a steel arc chamber in the middle.

Which demonstrate the basic components of a standard vacuum interrupter. The arcing contacts of modern versions of this interrupter are encircled by a metal shield.

The arc chamber and insulator diameters are matched with the diameters of the contacts and their stems. The use of metallic bellows allows the moving contacts to move.

A hermetically sealed interrupter is created by joining the arc chamber to the housing flange, which is then brazed to metalized ceramic insulators. Typically, the vacuum pressure is 10-6 bar.

  

Clearing and Closing time of a Circuit breaker - Below diagram shows the clearing and closing time of the circuit breaker. 

Applications of VCB

Vacuum circuit breaker has the following applications:

• Circuits with high voltage 
• Electrical substations and generators use it.
• Double earth faults and out of phase currents are interrupted.
• We use VCB for applications that require fast switching sequences.
• This circuit breaker is used in railway applications for traction current and electric supply switching.
• To turn on and off motor drives.

Electrical Interview questions and answers

1) What output power you will get from an ideal transformer and why?

An perfect transformer has no losses such as hysteresis loss, eddy current loss, and so on. As a result, an ideal transformer's output power is exactly equal to its input power. As a result, 100% efficiency.

2) What is transformer efficiency & all-day efficiency? What is the condition form maximum efficiency?

Transformer Efficiency: The transformer's efficiency is calculated by dividing the output power by the input power. Some of the input power is squandered in internal processing.

losses of the transformer.

Output Power / Input Power = Efficiency

All Day Efficiency:

All-day efficiency is defined as the ratio of energy delivered in Kilo Watt-Hour (kWh) to energy input in kWh of the transformer over a 24-hour period.

all_day = kWh output / kWh input

Condition for Maximum Efficiency:

The copper loss must equal the iron loss, which is the sum of hysteresis and eddy current losses.

Cu Loss = Iron Loss

Wcu = Wi

3) Why the current transformer’s secondary should not be open when there is current flowing in its primary?

On the secondary side, the current transformer is essentially a step-up transformer that increases the voltage while decreasing the current.When the secondary is open, the primary current becomes the magnetizing current, generating an extremely high secondary voltage that might damage the insulation and endanger personnel.

4) What will happen if DC supply is given to the primary of the Transformer?

Transformers have a high inductance and a low resistance. There is no inductance in a DC supply, therefore only resistance acts in the electrical circuit. As a result, a large electrical current will flow through the transformer's primary side. As a result, the coil and insulation will burn out.

5) What exactly is the distinction between an ammeter and a voltmeter?

Ammeter is a low resistance indicating instrument while the voltmeter is high resistance one.

6) Why should an ammeter have such a low resistance?

The ammeter connected in series with the circuit carrying the current under measurement must have a very low resistance so that the voltage drop across the ammeter and the power absorbed by the circuit are as low as possible.

7) Why should a voltmeter be of very high resistance?

Voltmeter, which is connected in parallel with the circuit across which the voltage is to be measured, must be of very high resistance so that the current flowing through The voltmeter and power consumed by the circuit are as low as feasible.

8) How can an ammeter be changed in to a voltmeter?

An ammeter with a low range can be transformed into a voltmeter by connecting it in series with a high resistance, providing the current through the series combination is within the ammeter's range when connected across the voltage under measurement.

9) What do you understand by the term ‘burden’ of a CT?

When the CT is supplying the instrument with its maximum rated current on the secondary side, the product of voltage and current is known as rated burden and is stated in volt-amperes.

10) What Is Skin Effect?

The current density of alternating current going through a conductor is very high near the surface and very low near the center of its cross-section area. This is known as the skin effect, and it is exactly proportional to frequency. As a result, stranded conductors are employed in power transmission.

 

11) How to reduce Skin Effect?

The methods of reducing skin effects are:

To lessen the skin effect, an ACSR bundled conductor is employed.

Using a cable material with a lower magnetic permeability.

The conductor's size is being reduced.

Increasing voltage by decreasing current, which reduces the skin effect in the same conductor.

 

13) What is Ferranti Effect?

The Ferranti effect occurs when the voltage at the receiving end of a transmission line is greater than the voltage at the sending end. This type of impact is caused primarily by a low load or an open circuit at the receiving end. The key properties of lines with a length of 240km or more are capacitance and inductance. The capacitance on such transmission lines is not concentrated at certain spots. It is evenly spread along the entire length of the line.

When a voltage is provided to the transmitting end, the current drawn by the line's capacitance exceeds the current connected with the load. As a result, at little or low load, the voltage at the receiving end is quite high in comparison to the constant voltage at the sending end.

14) How can we reduce Ferranti Effect?

Ferranti effect can be reduced:

By installing shunt compensation devices at receiving end. A shunt reactor linked in parallel with the transmission line serves as the compensation mechanism. It lowers the voltage by absorbing reactive power.

Running the transmission line with higher load. I.e if you have two line both carries 5 % load in each side means, we can switch of the one transmission line and the remaining load can be diverted in to another one.

15) What is Proximity Effect?

When high alternating voltage is applied to conductors, currents are not equally distributed across the cross-section area of the conductor. This is known as the proximity effect. The proximity effect causes the perceived resistance of the conductor to increase due to the presence of additional conductors conducting current in its vicinity.

16) How can we reduce Proximity Effect?

We can reduce proximity effect by:

Reducing the size of the conductor

Expanding  the space between the two conductors. Dummies, for example, are used in cable manufacture to shorten the distance between conductors.

We can lessen the proximity impact by decreasing the frequency and increasing the voltage. It is virtually impossible.

However, the frequency of the alternating current cannot be adjusted. However, we can increase the voltage further.

 

17) What is a system?

When a set of connected elements performs a given function, the group of elements is said to create a system. A system is also the interconnection of numerous components for a specific activity. Consider the automobile.

18) What is control system?

The Control System is any collection of mechanical or electronic components that maintains, regulates, or commands the behavior of the system via a control loop. It might range from a simple control device to a huge industrial control device used to control processes or machines.

19) What are the types of Control System? Explain.

There are two types of Control System-

1. Open loop control system.

2. Closed loop control system.

The term "open-loop control system" refers to a system in which the control action is independent of the desired output signal.

Examples include an automatic washing machine and an immersion rod.

A closed-loop control system is one in which control action is dependent on the desired output. 

Examples include an automatic iron, a servo voltage stabilizer, and an air conditioner.

20) What are the benefits and drawbacks of an open-loop system?

Advantages of the open-loop control system

o Open loop systems are simple.

o These are economical.

o Maintenance is minimal and straightforward.

Disadvantages of the open-loop control system

o Open loop systems are inaccurate.

o These systems are not reliable.

o These are slow.

o Optimization is not possible.

21) What are the advantages of Closed-Loop System?

Advantages of closed-loop systems

o Closed loop systems are more dependable.

o Closed loop systems are faster.

o Many variables can be handled simultaneously.

o Optimization is possible.

Disadvantages of closed-loop systems

o Closed loop systems are expensive.

o Maintenance is difficult.

o Installation is difficult for these systems.

 

 

Electrical Interview question and answers

1) What are the most typical reasons for transformer humming?

Stray magnetic fields force the enclosure and accessories to vibrate, generating electric hum around transformers. magnetostriction is a secondary source of vibration that arises when the core iron is subjected to magnetic fields and undergoes minute form changes.

The core generates transformer noise. The amount of noise is generally determined by the transformer's design.

2) What is the voltage regulation of the transformer & why is it important?

A transformer's voltage regulation is the percentage change in secondary voltage from no load to full load. The voltage regulation is 0 if the secondary voltage remains constant throughout the load. However, in practice, it changes with the power factor of the load.

The voltage regulation value determines the transformer's efficiency, thus it is ideal to use a transformer with low voltage regulation.

3) There is a Transformer and an Induction Machine. Those two have the same supply. For Which Device the load current will be maximum and why?

For same rating and same loading, the losses occurred in both devices will be different because of its construction and application.

1) Because the transformer, unlike an induction motor, has no moving parts, less magnetizing current is required for the same load action. Induction motors, on the other hand, have an air gap between their primary (stator) and secondary (rotor) windings, which requires greater magnetizing current due to higher leakage reactance than a transformer.

2) Windage losses will have to be compensated for by the induction motor. Because of the rotation of the rotor to generate the same output. As a result, the induction motor consumes more load current than the transformer.

4) How many types of cooling system are there in Transformers?

The types are

1. ONAN (oil natural,air natural).

2. ONAF (oil natural,air forced).

3. OFAF (oil forced,air forced).

4. ODWF (oil direct,water forced).

5. OFAN (oil forced,air forced).

 

5) What is an Ideal Transformer?

An ideal transformer is a fictitious transformer in which no losses occur. To put it another way, the transformer The input power is equal to the output power of the transformer, implying that they are 100% efficient. Because a real transformer must have some losses, it is only a theoretical transformer. Transformer power input = Transformer

Output Power.PIN = POUT. 

6) What is Plugging Breaking?

The supply connections are reversed in this approach, which causes the generator torque to reverse, which resists the usual rotation of the motor and causes the speed to drop. External resistance is also put into the circuit during plugging to reduce the flowing current. The biggest downside of this technology is that it wastes power.

7) What is dynamic breaking?

In this method of braking, the running motor is separated from the source and linked across a resistance. When the motor is unplugged from the power supply, the rotor continues to rotate owing to inertia, acting as a self-excited generator. When the motor is used as a generator, the current and torque flow reverse. Sectional resistances are cut out one by one during braking to maintain constant torque.

8) What Is Meant By Armature Reaction?

Armature reaction refers to the influence of armature flux on main flux. The armature flux influences the main field flux in two ways:The main field flux is distorted by the armature reaction.The magnitude of the primary field flux is reduced.

9) Which Motor Has High Starting Torque And Staring Current Dc Motor, Induction Motor Or Synchronous Motor?

The DC series motor has the highest beginning torque of any motor, which is why it is employed in electrical apparatus requiring strong starting torque, such as cranes and hoists.

10) What is a Universal Motor?

A universal motor can be powered by a direct current (DC) or a single phase alternating current (AC) supply. When a DC supply is connected to the universal motor, it operates as a DC series motor.An electromagnetic field is created when electricity travels through the field winding. The same current runs through the armature conductors as well. A mechanical force is experienced by a current carrying conductor when it is put in an electromagnetic field. The rotor begins to revolve as a result of this mechanical force, or torque. The direction of this force is determined by fleming's left hand rule.

It still creates unidirectional torque when powered by an alternating current supply. Because the armature and field windings are linked in series, they are in the same phase.As a result, as the polarity of the alternating current changes on a regular basis, the current direction in the armature and field winding reverses at the same time.

Thus, direction of magnetic field and the direction of armature current reverse in such a way that the direction of force experienced by armature conductors remains same. Thus, regardless of whether the power source is AC or DC, Universal Motors operate on the same principles as DC series motors.

 

Electrical Interview Questions and Answers

1) What is the difference between a single pole and a double pole circuit breaker?

Single-pole breakers have only one hot and one neutral wire. When an overload occurs in a single-pole breaker's circuit, only that breaker trips.

In double-pole breakers, two hot wires are linked by a single neutral wire. That is, if any of the poles' hot wires shorts out, both trip.

2) What Is the Difference Between Fuse And Breaker?

When the current exceeds the fuse's limit, a metal wire called the fuse link or element melts. It operates automatically and is a one-time use item that must be replaced.

A circuit breaker is an electro mechanical switch that opens the circuit in the event of an over current or short-circuit. It works both automatically and manually and can be used again simply resetting the lever.

3) What is the difference between circuit breaker & Isolator?

A circuit breaker, like a fuse, is a protective electromechanical device used to control the flow of current. In the event of a fault condition such as a short circuit or overload, it automatically breaks the circuit. It can also break the circuit manually. It is an ON-load and OFF-load device, which means it can operate in both ON and OFF supply conditions.

Isolator: An isolator is a mechanical switch used in substations to isolate or disconnect electricity supplies. It is an off-load device, which means it operates when the power supply is turned off.

4) Why Motor rated in kW instead of kVA?

The transformer is rated in KVA since its PF (Power Factor) is affected by the nature of the loads. However, the motor has a fixed power factor, i.e. the motor has a defined power factor (P.F) and the rating is stated on the motor in kW or HP. To put it another way, the motor only uses active electricity and provides mechanical power in HP or kW at the motor shaft, hence the motor rating in Watts.

5) What is the definition of generator & motor?

A machine that transforms electrical energy to mechanical energy is known as an electric motor. A motor's operation is based on a current-carrying conductor that experiences force when kept in a magnetic field. A machine that transforms mechanical energy to electrical energy is known as an electric generator. The generator's operation is based on electromagnetic induction.

6) What is a motor starter?

A motor starter is a device that connects in series with the motor to reduce the starting current (which, under normal conditions, could damage the winding) and gradually increase current after starting the motor (in other words, start or stop the motor) and offer overload safety.

7) What are the different methods for starting an induction motor?

The following methods are used to start an induction motor:

DOL: direct online starter

Star delta starter

Auto transformer starter

Resistance starter

Series reactor starter

8) What is the difference between a generator and an alternator?

Both the alternator and generator operate on the basis of Faraday's law of electromagnetic induction. An alternator is a device that converts mechanical energy into (alternating current) electrical energy. It always generates alternating current. Alternators have a high efficiency. A Generator is a mechanical device that converts mechanical energy into either alternating current  or direct current  electrical energy. It can produce alternating or direct current.Generators are thought to be less efficient. The primary distinction between an alternator and a generator is that in an alternator, the armature is stationary while the field spins, but in a generator, the armature rotates while the field remains stationary.

9) What Are The Advantages Of Star¬ Delta Starter With Induction Motor?

The following are the primary benefits of using a star delta starter:

To reduce the starting current required for the induction motor, which is 6 to 7 times higher than full load current and can damage the motor's windings.

To eliminate the voltage drop problem caused by the high starting current results in a voltage drop down the consumer line, which may cause harm to other electrical equipment.

Its operation is quite simple.

This beginning kit is rather inexpensive.

It has a strong torque-to-current ratio.

 

10) Why is the starting current high in dc motor?

There is no back emf in a dc motor. The resistance of the circuit controls the armature current when the motor starts. The armature has a low resistance, and when the entire voltage is provided to the motor while it is at rest, the armature current becomes extremely high, causing damage to the motor's components.

11) What is an induction motor's slip?

Slip is the percentage difference between an induction motor's synchronous speed Ns and rotor speed N. It is represented by the letter S. The induction motor's rotor speed is always smaller than its synchronous speed.

12) Why can't a series motor be started on no-load?

No load should never be applied to a series motor. Because there is no mechanical load on the series motor, the current is low, and the counter-EMF produced by the field winding is weak, therefore the armature must revolve faster to produce enough counter-EMF to balance the supply voltage. Over speeding might cause harm to the motor.

13) Explain the principle of Induction Motor.

To make a DC motor rotate, we must provide double excitation. We provide one supply to the stator and another to the rotor in a DC motor via a brush arrangement. However, because we only provide one supply in an induction motor, it is interesting to learn how an induction motor operates.

It is simple, from the name itself we can understand that here, the induction process is involved. When we turn on the power to the stator winding, a magnetic flux is created in the stator as a result of the current flowing through the coil. The rotor winding is constructed in such a way that each coil becomes short-circuited.

The flux from the stator short-circuits the rotor's short-circuited coil. According to Faraday's law of electromagnetic induction, when the rotor coils are short-circuited, current begins to flow through the rotor coil. When current goes through the rotor coils, additional flux is generated in the rotor.

There are now two fluxes, one stator flux and one rotor flux. The rotor flux will be slower than the stator flux. As a result, the rotor will experience torque, causing it to revolve in the direction of the revolving magnetic field. This is how single-phase and three-phase induction motors work.

14) What is the difference between a Four Point Starter and a Three Point Starter?

The starter which consist three terminals is known as the three point starter. The three-point starter's terminals are the armature, field, and line. The no-voltage coil (NVC) is linked in series with the field winding in the three-point starter.

The starter with four terminals is known as a four point starter. Along with the armature, field, and line terminals, a four-point starter has an extra terminal that connects the no voltage coil in parallel with the shunt field winding. The no-voltage winding is linked in parallel with the field winding in a four-point starter.

The three-point and four-point starters are built similarly. When the speed of the motor varies with a three-point starter, however, current flows through the field coil, affecting the no-voltage coil. The four-point starter is intended to alleviate the difficulty.

15) What Is Meant By Regenerative Braking?

When the motor's speed surpasses the synchronous speed, regenerative braking occurs. This baking method is known as regenerative braking because the motor acts as a generator and the supply receives power from the load, i.e. motors. The rotor must rotate faster than synchronous speed for regenerative braking to occur; only then will the motor operate as a generator, and the direction of current flow through the Circuit & torque direction reverse and braking occurs. The primary disadvantage of this sort of braking is that the motor must run at super synchronous speed, which may cause mechanical and electrical damage to the motor; however, regenerative braking can be performed at sub synchronous speed if a variable frequency source is provided.

Electrical Interview Questions and Answers

1) What is Electrical Engineering?

Electrical engineering is the branch of engineering that studies and applies electricity, electronics, and electromagnetism.

2) What is electricity ?

Electricity is a broad phrase that encompasses all phenomena induced by electric charge, whether static or moving.

3) What are the types of electricity ?

There are two types,(1) Static Electricity and (2) Current Electricity.

4) What is static electricity ?

Static electricity is electricity at rest, as opposed to dynamic or current electricity, the effects of which are solely due to the charge's electrostatic field. It is also known as frictional electricity since it is created by rubbing two substances such as glass and silk together.

5) What is current electricity ?

Current electricity is defined as electricity in motion, the effects of which are caused by electron flow in a conductor.

6) What are the many types of current electricity?

There are two kinds of current: (1) direct current and (2) alternating current.

7)What are the many methods of generating electricity? Give some examples.

The methods are as follows:

i) Static electricity is produced by frictions.

ii) Through chemical reactions in cells and batteries.

iii) Through mechanical driving- A generator generates electricity in two distinct ways.

iv) Heat is used to generate thermal electricity.

v) Using the lighting effect - Electricity is generated in a photoelectric cell.

8) Explain the difference between direct and alternating current?

The movement of electric charge in only one direction is referred to as direct current (DC). It is the constant-voltage circuit's steady state.The flow of electric charge that alternately reverses direction is known as alternating current (AC). If the source varies on a regular basis, especially if it is sinusoidal, the circuit is known as an alternating current circuit.

9) Where is D.C. used ?

1)Battery charging 

2)Electroplating 

3)Electrolysis 

4)Relays 

5)Traction motors

10) Where is A.C. used ?

1)Home appliances

2)Fans

3)Refrigerators

4)Power driving motors. 

5)Radio and television set

11) What is active, reactive, apparent & complex power?

1) Active power: This is the real power given to the load, such as a transformer, induction motor, generator, and so on, and dissipated in the circuit. It is indicated by the letter P, and its unit is watts W.

2) Reactive Power: Reactive power is the power that constantly bounces back and forth between the source and the load. It is represented by the letter Q, and its unit is VAR voltage-ampere reactive.

3) Apparent Power: It is the product of voltage and current without taking into account the phase difference. It is a hybrid of active and reactive power. It is represented by the letter S and its unit is the Volt-Ampere, or VA.

4) Complex power is the product of voltage and current with reference to their phase difference. It is the Vector or Complex sum of active and reactive power. It is represented by S and measured in VAR.

12) What is a leading & lagging power factor & how can you improve it? State the methods of power factor correction?

The cosine of the angle created by voltage and current is defined as the Power factor. A leading power factor occurs when the current exceeds the voltage. When current lags behind voltage, the power factor is lagging.Most loads are inductive, resulting in a trailing power factor. As a result, the following approaches are employed for p.f correction (to cancel out the lagging current):

1) Static Capacitor

The capacitor contributes to the provision of a leading current, which removes the trailing component of current and enhances the power factor.

2) Synchronous Condenser

It is a non-loaded over-excited synchronous motor with a leading power factor.

3) Phase Advancer

A phase advancer is a simple AC exciter that is linked to the main shaft of the motor and works with the motor's rotor circuit to boost power factor.

13) Why do we improve the power factor?

The following are the reasons for enhancing the power factors:

Large Line Losses (Copper Losses): Line losses (I2R) are current-dependent. When opposed to the high power factor, the low power factor draws a huge quantity of current.

Large kVA rating and equipment size: PF is inversely proportional to KVA. Low PF equipment with a high KVA rating takes up more space.

Large Conductor Size and Cost: Due to the poor power factor, we need large conductors to convey the heavy current required.

Poor Voltage Regulation and High Voltage Drop: The high current caused by low PF creates a high voltage drop that requires more frequent regulation than usual.

Low Efficiency : The losses due to the high current flow & voltage drop deteriorate the efficiency of the system. The efficiency is maximum at PF=1.

14) What is a unilateral & bilateral circuit?

A unilateral circuit is one whose attributes change depending on the direction of current flow or voltage. The parameters of a bilateral circuit do not alter when the current direction or supply voltage are changed.

15) What is a linear & non-linear circuit?

The relationship between current and voltage in a linear circuit is linear, i.e. directly proportional. With fluctuating current and voltage, circuit parameters like as frequency, resistance, inductance, capacitance, and so on stay constant.

The current and voltage do not have a linear relationship in a non-linear circuit. The electrical characteristics of such circuits change as the voltage and current vary.

16) What may cause the current in a linear circuit to double?

The current should be increased for two reasons:

1) Either half the total resistance of the circuit is lowered.

2) Alternatively, the circuit's supply voltage is doubled.

17) Why is Battery Rating in Ah (Ampere hour) and not in VA or Watts?

The charge contained inside the compounds is converted into electrical energy by a battery. The amount of current it can deliver is for a specific amount of time, hence the unit for its rating is Ampere-hour Ah. While batteries provide direct current with no phase or frequency, there is no idea of P.F or reactive power, therefore there is no need to describe it in VA and it is rated in Ah.

18) What is a primary & secondary cell?

The primary cell is a non-rechargeable battery that can never be recharged. They are disposable and cannot be utilized once completely charged. They are typically found in toys, handheld devices, and remote controls, among other things.

The secondary cell is a rechargeable battery that can be recharged hundreds of times (depending on the life cycle of the battery). Their initial cost is higher than that of the primary cell. They are mostly found in cell phones, autos, generators, and other similar devices.

19) What are the limitations of ohm’s law?

Ohm law does not apply to a unilateral or non-linear circuit. The criteria for ohm's law is that the resistance must be constant and temperature dependent. A non-linear or unilateral circuit's resistance varies with voltage and current. As a result, it is inapplicable not such a circuit. The temperature must also remain steady.

20) Does current lead or lag the voltage in an inductive or capacitive circuit?

In an inductive circuit, current lags behind voltage, whereas current leads voltage in a capacitive circuit.

21) Define the term Capacitance and Inductance? 

Capacitance is a component's ability to store charge between two plates when a potential difference is applied. It is symbolized by the letter C and is measured in Farads F.

Inductance is the ability of a conductor to resist or oppose changes in current. The current creates a magnetic field, the strength of which changes with the current. It is represented by the letter L and is measured in Henry H.

22) Why the Capacitors works on AC only?

In general, a capacitor provides infinite resistance to dc components (that is, it blocks the dc components). It enables ac components to pass through.

23) What is the maximum power transfer theorem?

It defines the specifications for maximum power transfer from source to load. It asserts that the maximum power will be transferred from source to load in a linear, bilateral network when the exterior load resistance matches the internal resistance of the source or the circuit's Thevenin's resistance.

24) Explain Thevenin’s Theorem in a single sentence.

Thevenin’s theorem states that any linear electrically complex circuit is reduced into a simple electric circuit with one voltage and resistance connected in series.

25) Explain Norton’s Theorem in a single sentence.

According to Norton's Theorem, any linear circuit, no matter how complex, can be simplified to an equivalent circuit with only a single current source and parallel resistance coupled to a load.

26) Explain Network Theorem.

Any element of a network's current or voltage is equal to the algebraic sum of the currents or voltages produced separately by each source. In other words, this theorem permits us to solve a current or voltage problem utilizing only one source at a time.

27) What is the working principle of a circuit breaker?

A circuit breaker is a device that either makes or breaks a circuit. It features two types of contacts: fixed and movable. Under typical conditions, the moving contact makes contact with the stationary contact, providing a closed contact for current flow. An arc forms between the fixed and movable contacts during abnormal and faulty conditions (when current exceeds the rated value), resulting in an open circuit. Arc Quenching media such as air, oil, vacuum, and so on extinguish the arc.

28) What Is a Vacuum Circuit Breaker?

By opening the contact terminals, a circuit breaker cuts the circuit. During the opening, an arc is formed between the terminals, which can be quenched using a variety of media. The medium for arc quenching in VCB is a vacuum. When opposed to air, vacuum has a higher voltage arc quenching ability and is employed in high voltage circuits.

29) What is the difference between MCB & MCCB?

The MCB stands for "miniature circuit breaker" and is used for current ratings of less than 100 amps and interrupting rates of less than 18k Amps. Its tripping properties are not adjustable, and it is employed for home reasons.

The MCCB is an abbreviation for "Molded case circuit breaker." It has a high current rating of roughly 2500 Amps and interrupting ratings ranging from 10K to 200K Amps. Its tripping properties can also be changed. They are widely utilized in industry.