Digital signals

Signal is defined as a function of dependent variables of independent varisbles
Or
Signal is a  quantity which carries the information
The independent variables are Time, Distance and etc
Signal can be one dimensional or two dimensional or many dimensional.
Signal can devide as ANALOGUE SIGNAL and DIGITAL SIGNAL.
Again Analogue signal divided as CONTINUOUS TIME SIGNALS and DISCRETE TIME SIGNALS
Note
All continuous signals are Analogue signals buy all Analogue signals are not continous signals

Motor inner parts

ANATOMY

Result if we connect d.c motor to a.c supply

What happens when a d.c motor is connected across an ac supply?

A) *.Since on ac supply, reactance will come in to play,the a.c supply will be offered impedance(not resistance) by the armature winding. consequently,with a.c supply,current will be much less.The motor will run but it would not carry the same load as it would on d.c. supply.
*.There would be more sparking at the brushes
*.Though motor armature is laminated as a rule, the field poles are not. consequently,eddy currents will cause the motor to heat up eventually burn on a.c. supply

REF relay

What is REF relay?

A) It is restricted earth fault relay. When the fault occurs very near to the neutral
point of the transformer, the voltage available to drive the earth circuit is very small,which may not be sufficient to activate the relay, unless the relay is set for a very low current.
Hence the zone of protection in the winding of the transformer is restricted to cover only around 85%. Hence the relay is called REF relay.

 

Difference between generator and alternator

State the difference between generator and alternator

Ans: Generator and alternator are two devices, which converts mechanical energy into electrical energy. Both have the same principle of electromagnetic induction, the only difference is that their construction.
Generator persists stationary magnetic field and rotating conductor which rolls on the armature with slip rings and brushes riding against each other, hence it converts the induced emf into dc current for external load whereas an alternator has a stationary armature and rotating magnetic field for high voltages but for low voltage output rotating armature and stationary magnetic field is used

 

Ratings of synchronous generator and Alternator

 Why rating of Synchronous Generators and Alternators in MVA or KVA?

A: Normally the rating of synchronous generators or alternators will be in KVA or MVA instead of kW rating.
Electrical apparatus or machines are usually rated the load which it can carry without overheating and damaging to insulation. i.e, rating of the electrical machines are governed by the temperature rise caused by the internal loss of the machine. The copper loss in the armature depends on the strength of the armature current and core loss depends on voltage and these losses are independent of the power factor.
The reason for which the transformers and synchronous generators are rated in volt-amperes instead of watts is that manufacturer does not know at what power factor does these equipments are going to operate. On the other hand while manufacturing the motors manufacturer specifies the power factor at which the motor should be operate. This is the reason why the motor loads (including synchronous motors are rated in kw) are rated in wattage power.
In the case of alternator and transformers manufacturer

does not know the operating power factor. Hence they are rated in KVA or MVA

 

Auto transformer

Autotransformer:

An autotransformer is an electrical transformer in which there is one winding, a portion of which is common to both the primary and the secondary circuits. In other words, the primary and secondary coils have some or all windings in common.

An autotransformer is commonly used for the voltage conversion of local power line voltage to some other Voltage value needed for a particular piece of electrical equipment. Most often, this conversion is from 125 Volts to 250 Volts, or 250 Volts to 125 Volts.

Unlike an isolation transformer, an autotransformer uses common windings and offer no interference or disturbance isolation.

A given size autotransformer will support a load equal to its rated value whether it is connected in the 125 Volts to 250 Volts configuration, or in the 250 Volts to 125 Volts configuration.

These units are employed in custom designs or when converting industrial/military equipment between various operating voltage systems. Most often, this conversion is from 125 Volts to 250 Volts, or 250 Volts to 125 Volts.

Unlike an isolation transformer, it uses common windings and offer no interference or disturbance isolation. You add any suppression or filtering networks your system requires.

With a single tapped winding, an autotransformer is generally preferred to an isolation transformer, with two separate windings, for numerous reasons. It is much smaller and lighter than an isolation transformer. It also has better voltage stability and greater overload tolerance. It performs in much the same way as the electrical transformer that the electric utility uses to bring power to a building.

An autotransformer is a tapped winding transformer that changes the voltage available locally to the voltage required by a particular load. Thus, a load may operate anywhere around the world, as long as a transformer is available to convert the local voltage to the voltage it requires.

"Variac" is a trademark of General Radio (mid-20th century) for a variable autotransformer intended to conveniently vary the output voltage for a steady AC input voltage.
The term is often used to describe similar variable autotransformers made by other makers. An autotransformer is an efficient and quiet method for adjusting the voltage to incandescent lamps.

While lightweight and compact semiconductor light dimmers have replaced variacs in many applications such as theatrical lighting, these transformers are still used when an undistorted variable voltage sine wave is required.

Defination of reactive power

Defination of Reactive power :



Real power is that portion of apparent power,which is consumed resitive portion of the ckt. We can see d result of this consumed power,as heat,rotation,light etc.Reactive power is that portion of apparent power,which is not consumed by load. Reactive components store energy in positive half cycle, & release energy in negative half cycle. We can see this reactive power as magnetism in inductor & as voltage in capacitor.

Pole face of d.c machine

Why are the pole faces of dc machine kept curved i.e. circular???

 

et,we have used plane face pole. Distance between pole & rotor will minimum in the middle of pole, and maximum in the edge of the pole. So,magnetic fld intensity will vary to the conductor of armature. But,we need to provide a constant fld. To do this,we should make the gape betwn pole & rotor constant. As,rotor is circular,so pole should be circular.

Importance of flourescent coating in tube light

What will happen,if we don't use flourescence coating in tube light??

In tube light,marcury(Hg) gas is used. When,using choke coil, sufficient voltage is generated across tube light,this gas will be ionized, & emit ultra violate ray. This ultra violate ray struck the flourescence coating(f.c.). Now,f.c. will emit visible light (nature of emitted light depends on their bandgap).

*so,without f.c. ultra violet ray will emitted from light.

Different frequencies and different voltage levels

Why different frequencies and different voltage levels for electrical supply systems around the world??

Europe and most other countries in the world use a voltage which is twice that of the US. It is between 220 and 240 volts, whereas in Japan and in most of the Americas the voltage is between 100 and 127 volts.

The system of three-phase alternating current electrical generation and distribution was invented by a nineteenth century creative genius named Nicola Tesla. He made many careful calculations and measurements and found out that 60 Hz (Hertz, cycles per second) was the best frequency for alternating current (AC) power generating. He preferred 240 volts, which put him at odds with Thomas Edison, whose direct current (DC) systems were 110 volts. Perhaps Edison had a useful point in the safety factor of the lower voltage, but DC couldn't provide the power to a distance that AC could.

When the German company AEG built the first European generating facility, its engineers decided to fix the frequency at 50 Hz, because the number 60 didn't fit the metric standard unit sequence (1,2,5). At that time, AEG had a virtual monopoly and their standard spread to the rest of the continent. In Britain, differing frequencies proliferated, and only after World War II the 50-cycle standard was established. A big mistake, however.

Not only is 50 Hz 20% less effective in generation, it is 10-15% less efficient in transmission, it requires up to 30% larger windings and magnetic core materials in transformer construction. Electric motors are much less efficient at the lower frequency, and must also be made more robust to handle the electrical losses and the extra heat generated. Today, only a handful of countries (Antigua, Guyana, Peru, the Philippines, South Korea and the Leeward Islands) follow Tesla’s advice and use the 60 Hz frequency together with a voltage of 220-240 V.

Originally Europe was 110 V too, just like Japan and the US today. It has been deemed necessary to increase voltage to get more power with less losses and voltage drop from the same copper wire diameter. At the time the US also wanted to change but because of the cost involved to replace all electric appliances, they decided not to. At the time (50s-60s) the average US household already had a fridge, a washing-machine, etc., but not in Europe.

The end result is that now, the US seems not to have evolved from the 50s and 60s, and still copes with problems as light bulbs that burn out rather quickly when they are close to the transformer (too high a voltage), or just the other way round: not enough voltage at the end of the line (105 to 127 volt spread !).

Note that currently all new American buildings get in fact 230 volts split in two 115 between neutral and hot wire. Major appliances, such as ovens, are now connected to 230 volts. Americans who have European equipment, can connect it to these outlets

Difference between generator and alternator

Interview question:

State the difference between generator and alternator

Answer:
Generator and alternator are two devices, which converts mechanical energy into electrical energy. Both have the same principle of electromagnetic induction, the only difference is that their construction.
Generator persists stationary magnetic field and rotating conductor which rolls on the armature with slip rings and brushes riding against each other, hence it converts the induced emf into dc current for external load
whereas an alternator has a stationary armature and rotating magnetic field for high voltages but for low voltage output rotating armature and stationary magnetic field is used.

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EEE Interview Question

Noload power factor is very low

During No load why the power factor of the transformer is very low ?

■ Ans: Current flowing through the transformer consists of two components. Magnetizing current (Im) which is in quadrature (900) to the applied voltage and in phase current which is in phase to the applied voltage. During no load condition most of the excitation current drawn by the transformer from the primary winding is to magnetize the path. Hence excitation current drawn by the transformer during no load condition mostly consists of magnetizing component of current which is used to provide magnetic field in transformer circuits (Inductive nature). Therefore as the nature of the load is inductive, hence the power factor of transformer during no load condition will by in the order of 0.1 to 0.2

D.C generator working and construction

 DC Generator working and construction details:

A shunt-wound DC generator is constructed so that the field winding is in parallel with the armature winding. The voltage of a shunt-wound DC generator decreases with an increase in load current. A series-wound DC generator is constructed so that the field winding is in series with the armature winding. The voltage of a series-wound DC generator increases sharply with an increase in load. In a cumulatively-compounded DC generator, the series and shunt fields aid one another. In a differentially-compounded DC generator, the series and shunt fields oppose one another. The voltage of a flat-compounded DC generator changes less than 5 percent from no-load to full-load. The voltage of an over-compounded DC generator gradually rises with an increasing load.

Here is the construction diagram of dc generator

An electrical generator is a device that converts mechanical energy to electrical energy, generally using electromagnetic induction. The source of mechanical energy may be a reciprocating or turbine steam engine, water falling through a turbine or waterwheel, an internal combustion engine, a wind turbine, a hand crank, or any other source of mechanical energy.

The Dynamo was the first electrical generator capable of delivering power for industry. The dynamo uses electromagnetic principles to convert mechanical rotation into an alternating electric current. A dynamo machine consists of a stationary structure which generates a strong magnetic field, and a set of rotating windings which turn within that field. On small machines the magnetic field may be provided by a permanent magnet; larger machines have the magnetic field created by electromagnets.

The energy conversion in generator is based on the principle of the production of dynamically induced e.m.f. Whenever a conductor cuts magneticic flux , dynamically induced e.m.f is produced in it according to Faraday's Laws of Electromagnetic induction.This e.m.f causes a current to flow if the conductor circuit is closed. Hence, two basic essential parts of an electrical generator are (i) a magnetic field and (ii) a conductor or conductors which can so move as to cut the flux.

Generator Construction:

Simple loop generator is having a single-turn rectangular copper coil rotating about its own axis in a magnetic field provided by either permanent magnet or electro magnets.In case of without commutator the two ends of the coil are joined to slip rings which are insulated from each other and from the central shaft.Two collecting brushes ( of carbon or copper) press against the slip rings.Their function is to collect the current induced in the coil. In this case the current waveform we obtain is alternating current ( you can see in fig). In case of with commutator the slip rings are replaced by split rings.In this case the current is unidirectional.

Components of a generator:

Rotor: In its simplest form, the rotor consists of a single loop of wire made to rotate within a magnetic field. In practice, the rotor usually consists of several coils of wire wound on an armature.

Armature: The armature is a cylinder of laminated iron mounted on an axle. The axle is carried in bearings mounted in the external structure of the generator. Torque is applied to the axle to make the rotor spin.

Coil: Each coil usually consists of many turns of copper wire wound on the armature. The two ends of each coil are connected either to two slip rings (AC) or two opposite bars of a split-ring commutator (DC).

Stator: The stator is the fixed part of the generator that supplies the magnetic field in which the coils rotate. It may consist of two permanent magnets with opposite poles facing and shaped to fit around the rotor. Alternatively, the magnetic field may be provided by two electromagnets.

Field electromagnets: Each electromagnet consists of a coil of many turns of copper wire wound on a soft iron core. The electromagnets are wound, mounted and shaped in such a way that opposite poles face each other and wrap around the rotor.

Brushes:The brushes are carbon blocks that maintain contact with the ends of the coils via the slip rings (AC) or the split-ring commutator (DC), and conduct electric current from the coils to the external circuit.

How DC generator works?

The commutator rotates with the loop of wire just as the slip rings do with the rotor of an AC generator. Each half of the commutator ring is called a commutator segment and is insulated from the other half. Each end of the rotating loop of wire is connected to a commutator segment. Two carbon brushes connected to the outside circuit rest against the rotating commutator. One brush conducts the current out of the generator, and the other brush feeds it in. The commutator is designed so that, no matter how the current in the loop alternates, the commutator segment containing the outward-going current is always against the "out" brush at the proper time. The armature in a large DC generator has many coils of wire and commutator segments. Because of the commutator, engineers have found it necessary to have the armature serve as the rotor(the rotating part of an apparatus) and the field structure as the stator (a stationary portion enclosing rotating parts).

Motor inner parts

Motor inner parts 

Wave energy system

wave Energy System:

The wave Energy System developed in Australia by BioPower Systems, harnesses the power of ocean waves and converts it into smart grid-connected electricity.

Which method can bring the locomotive to dead stop

# which method can bring the locomotive to dead stop.

(a) Plugging braking
(b) Rheostatic braking
(c) Regenerative braking
(d) None of the above

 

Answer : plugging for dc motor except for dc series motor

            for d.c series motor dynamic breaking is used

Difference between ground and neutral

What is the main difference between Ground and Neutral?

Answer:
The difference between Ground and Neutral? NEUTRAL is the origin of all current flow. In a poly-phase system, as its phase relationship with all the three phases is the same, (i.e.) as it is not biased towards any one phase, thus remaining neutral, that’s why it is called neutral. Whereas, GROUND is the EARTH on which we stand. It was perceived to utilize this vast, omnipresent conductor of electricity, in case of fault, so that the fault current returns to the source neutral through this conductor given by nature which is available free of cost. If earth is not used for this purpose, then one has to lay a long. long metallic conductor for the purpose, thus increasing the cost. Ground should never be used as neutral. The protection devices (eg ELCB, RCD etc) work basically on principle that the phase currents are balanced with neutral current. In case you use ground wire as the neutral, these are bound to trip if they are there – and they must be there. at least at substations. And these are kept very sensitive i.e. even minute currents are supposed to trip these. One aspect is safety – when someone touches a neutral, you don’t want him to be electrocuted – do you? Usually if you see the switches at home are on the phase and not neutral (except at the MCB stage). Any one assumes the once the switch is off, it is safe (the safety is taken care of in 3 wire system, but again most of the fixtures are on 2 wire) – he will be shocked at the accidental touching of wire in case the floating neutral is floating too much.

Transformer rating in kva

Why transformer rating is in KVA?

A transformer is basically rated in Kilovolt-amperes (kVA). An example is a 10 kVA Single phase Transformer, by which, the rating is 10 kVA. Have you wondered why transformers are rated in kVA and not in Kilowatts (kW)?
If we dig deeper into the study of transformers, we will see that the copper loss of a transformer depends on the current, while its iron loss depends on its voltage. Therefore, the total transformer loss, which is the copper loss and the iron loss, depends on the volt-ampere and not on the phase angle between current and voltage. Thus, the transformer losses are independent on the load power factor. It is the main reason why transformers are rated in kVA and not in kW.

Single phase transformer

CLEAR EXPLANATION OF SINGLE PHASE TRANSFORMER

Basic Parts of the Distribution transformer

In Transformers Part 1, a transformer was defined as a stationary equipment which transforms power from one voltage level to another through electromagnetic induction. After learning the theory of operation of transformers, it is necessary to know the basic parts of an electrical transformer. Take note that the transformer used in my example is a single phase distribution transformers. These are transformers mostly mounted on pole to deliver power to residential and commercial establishments.
As shown in the figure, the basic parts of a distribution transformer are as follows:
A.  Hand Hole –The hand hole, as the name implies, serves as an access point of a technician to tap changers/mechanisms located  inside the tank without the need of opening the cover. Most modern transformers have tap changers located outside the tank for convenience.
B. Lifting Lugs – This is used, where the hook/rope is connected, for lifting, either using a hoist or a crane.
C. Terminal Markings (Secondary) – The markings provide identification about the terminals of a transformer.
D. LV Bushing – The bushing is made of porcelain. It serves as the output and is the low voltage side of the transformer, which usually supplies power on residential/commercial establishments.
E. Ground Tap – As the name implies, this is where the grounding of the transformer is connected.

F. Transformer Markings – Are markings which indicate the capacity (in Kilovolt-amperes) of a transformer and its voltage output.
G. Radiator Fins –This is the cooling mechanism of a transformer. The cooling mechanism of a transformer depends on the size or rating of the transformer. The bigger the rating, the more cooling mechanisms are used. Take note that in order to maintain operation of the transformer for a long period of time, it is necessary to keep the temperature to be stable.
H. Casing (Tank) – It is generally made of steel. It encloses the core-coil and is the container for the liquid coolant/insulant.
I. HV Bushing – This is the bushing for the high voltage side of the transformer. It is usually made of solid porcelain. This is the input of the transformer.
J. Pressure Relief Device – This is a spring loaded device which releases excess pressure.
K. Mounting Lugs – This is usually used if the transformer is mounted on poles. It is connected on a transformer cluster which is connected on a pole.
L. Tap Changer – This sets the ratio of the HV and LV windings. Most distribution transformers have taps ± 5%, ± 2.5% and 0.
M. Nameplate – Contains all data about the distribution transformer it is connected to.
N. Core – Part of a transformer that serves as a path for the flow of magnetic flux. There are two types of transformer core, the Shell type and the Core type. The core is inside the tank.
• Core Type – The core is in the form of a rectangular frame with coils placed on two vertical sides. They are divided, part of each primary and secondary on each of the two vertical legs.
• Shell Type – The core surrounds the coils, instead of the coils surrounding the core.
O. Windings – Arrangement of conductors wound on an insulating form with each turn insulated from all the other turns. This usually determines the rating of the transformer as the winding is designed by the amount of current it can carry.

Construction details of single phase transformer

CLEAR EXPLANATION OF SINGLE PHASE TRANSFORMER

# The major cause of creeping in an energymeter is

A. over compensation for friction
B. excessive voltage across potential coil
C. mechanical vibrations
D. stray magnetic field

A future where the whoosh of passing cars power highway lights

#‎In‬ distribution transformer which winding is used

A. helical
B. sandwitched
C. circular
D. cylindrical

 

# Swinburne’s test is applicable to

A. DC series motor
B. DC shunt motor
C. DC compound motor
D. None of the above

Extra high Voltage Oil filled Cable (110kV/500kV)

Constructional differences between rotors

why do transformers make a humming sound??

Answer:

Iron or ferrite core transformers if operate at frequency between 20- 20,000 Hz of the applied ac voltage,
the core material's length is extended & contracted in length by very small amount at that frequency known as magnetostriction process.
Magnetostriction causes air being pushed back & forth at that frequency causing sound generation which is hummung sound.
Transformers without core do not generate that sound

How the engineer see the society

how the engineer see the society
v

Temperature sensor

Temparature sensor

Capacitor voltage transformer

Capacitor Voltage Transformers/ Coupling Capacitors

What is reverse power relay?

Answers:-
Reverse Power flow relay are used in generating stations's protection. A generating stations is supposed to fed power to the grid and
in case generating units are off, there is no generation in the plant then plant may take power from grid.
To stop the flow of power from grid to generator we use reverse power relay.

interview question:

Two bulbs of 100w and 40w respectively connected in series across a 230v supply which bulb will glow bright and why?

Answers:-
Since two bulbs are in series they will get equal amount of electrical current but as the supply voltage is constant across the bulb(P=V^2/R).
So the resistance of 40W bulb is greater and voltage across 40W is more (V=IR) so 40W bulb will glow brighter

Capacitor Voltage Transformer(CVT):

A capacitor voltage transformer (CVT) is a transformer used in power systems to step down extra high voltage signals and provide a low voltage signal, for measurement or to operate a protective relay.
The device has at least four terminals: a terminal for connection to the high voltage signal, a ground terminal, and two secondary terminals which connect to the instrumentation or protective relay.

The CVT is also useful in communication systems. CVTs in combination with wave traps are used for filtering high frequency communication signals from power frequency.

Capacitor

Q : How do capacitors store a charge?

Answer: Capacitors act like tiny storage batteries made of two plates separated by a thin insulator or air. When one plate is charged negative and the other positive, they build up a charge that remains when the current is removed. When its power is required, the circuit is switched to conduct current between the two plates, and the capacitor releases its charge. AnswerCapacitors don't really store charge at all. They allow negative charge to be transferred from one plate to the other, thus establishing an electric field between their plates. But there is no net increase in charge -the amount of charge on the capacitor's plates, after 'charging', is exactly the same as there was before 'charging' -it's just moved around! What capacitors 'store' is energy, not charge.

interview question:

Why synchronous generators are used for the production of electricity?

Answers:-
synchronous machines have capability to work on different power factor (or say
different imaginary power varying the field emf.)
Hence syn. generators r used for the production of electricity.

New technology:

Marine Solar Cells (MSC) by Phil Pauley are conceptual hybrid solar and wave energy generators designed to generate renewable energy off shore.
The solar wave unit captures wave energy through natural buoyancy displacement and solar energy through photovoltaic cells, taking advantage of natural light reflecting off the ocean’s surface to increase solar capture by 20%.
This ability contrasts with conventional solar farms or wave power designs which only harvest one form of power

# If the no. of rotor slots is equal to no.of stator slots, then motor refuses to start.
Hence it is known as

A. crawling
B. cogging
C. air gap
D. relative speed




Answer : cogging

Grounding transformer

Grounding Transformer:

A Grounding Transformer is used to provide a physical neutral for a power transformer with a delta connected downside.
The Grounding Transformers neutral point has low impedance and is suitable for different system groundings such as solid earthing, NER earthing (resistor) and resonance earthing (Arc Suppression Coils).

The Grounding Transformer can also be equipped with a low voltage auxiliary winding to be used as local power supply to the substation.

# The direction of rotation of a D.C. series motor can be changed by

A. Interchanging supply terminals
B. Interchanging field terminals
C. both (A) and (B)

Answer : c but one only at a time

# To improve the efficiency of thermal power plant ————————is placed between boiler and turbine.

A. ash handling point.
B. air pre-heater.
C. economizer.
D. super heater.



Answer : super heater

Latest Invention:
"Wind Lens - Structure" that Triples the Power of Wind Turbines

The Wind Lens functions similar to a magnifying glass that increases the light from the sun.
the structure features a hoop that is used to increase wind power, and a turbine that rotates by making use of the wind captured from the hoop.

 Wind turbine and its internal parts

● Ques: What is 2 phase motor?

● Ans: A two phase motor is often a motor with the the starting winding and the running winding have a phase split. e. g; ac servo motor. where the auxiliary winding and the control winding have a phase split of 90 degree.

● Ques:What is slip in an induction motor?

● Ans:Slip can be defined as the distinction between the flux speed (Ns) and the rotor speed (N). Speed of the rotor of an induction motor is always less than its synchronous speed. It is usually expressed as a percentage of synchronous speed (Ns) and represented by the symbol ‘S’.

Ques:Why we can’t store AC in Batteriesinstead of DC.or Can we store AC in batteries instead of DC?

Ans:We cannot store AC in batteries because AC changes their polarity upto 50 (When frequency = 50 Hz) or 60 (When frequency = 60 Hz) times in a second. Therefore the battery terminalskeep changing Positive (+ve) becomes Negative (-Ve) and vice versa, but the battery cannot change their terminals with the same speed so that’s why we can’t store AC| in Batteries.
Also when we connect a battery with AC Supply, then It will charge during positive half cycle and discharge during negative half cycle because the Positive(+ve) half cycle cancel the negative (-Ve) half cycle, so the average voltage or current in a complete cycle is Zero. Sothere is no chance to store AC in the Batteries.
Also note that Average Voltage x Average Current ≠ Average Power

Difference between AC & DC power supply




Ques:Why we can’t store AC in Batteriesinstead of DC.or Can we store AC in batteries instead of DC?

Ans:We cannot store AC in batteries because AC changes their polarity upto 50 (When frequency = 50 Hz) or 60 (When frequency = 60 Hz) times in a second. Therefore the battery terminalskeep changing Positive (+ve) becomes Negative (-Ve) and vice versa, but the battery cannot change their terminals with the same speed so that’s why we can’t store AC| in Batteries.
Also when we connect a battery with AC Supply, then It will charge during positive half cycle and discharge during negative half cycle because the Positive(+ve) half cycle cancel the negative (-Ve) half cycle, so the average voltage or current in a complete cycle is Zero. Sothere is no chance to store AC in the Batteries.
Also note that Average Voltage x Average Current ≠ Average Power

# What will happen when power factor is leading in distribution of power?

Answers:-
If their is high power factor, i.e if the power factor is close to one:

1.losses in form of heat will be reduced,
2.cable becomes less bulky and easy to carry, and very
cheap to afford, &
3. it also reduces over heating of tranformers.

Comment If you Are Genius !!!!

*In a network made up of linear resistors and ideal voltage source values of resistors are doubled. Then the voltage across each resistor is

A. doubled
...

Sodium vapour lamps

Difference between electronic regulator and ordinary regulator for fan

interview question:
what is the diff. btwn. electronic regulator and ordinary rheostat regulator for fans?

Answer:-

The difference between the electronic and ordinary regulator is that in electronic reg. power losses are less because as we decrease the speed the electronic reg. give the power needed for that particular speed but in case of ordinary rheostat type reg. the power wastage is same for every speed and no power is saved.In electronic regulator triac is employed for speed control by varying the firing angle speed is controlled but in rheostatic control resistance is decreased by steps to achievespeed control