What is Electric Field in Hindi

Electric Field theory:-

 It is found that in the medium around a charge a force acts on a positive or negative charges when placed in that medium. If the charge is sufficiently large, then it may create such a huge stress as to cause the electrical rupture of the medium, followed by the passage of an arc discharge.

Attraction 

The region in which the stress exists or in which electric forces act, is called an Electric Field or Electrostatic field.

 The stress is represented by imaginary lines of forces. The direction of the lines of force at any point is the direction along which a unit positive charge placed at that point would move if free to do so.

It was suggested by Faraday that the electric field should be imagined to be divided into tubes of force containing a fixed number of lines of force.

Electric field repulsion

He assumed these tubes to the elastic and having the property of contracting longitudinally the repelling laterally. With the help of these properties ,it becomes easy to explain .....
1) why unlike charges attract each other and try to come nearer to each other
2)why like charges repel each other.

However it is more common to use the term lines of force.
These lines are supposed to emanate from a positive charge and end on a negative charge .these lines always leave or enter a conducting surface normally.



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What is Static Electricity (Electrostatics)



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Laws of Electrostatics

 Laws of Electrostatics:-

There are two laws of electrostatics,as under...

 First Law:-

Like charges of electricity repel cach other, whereas unlike charges attract each other

Second Law:-

 According to this law, the force exerted between two point charges--
A) is directy the proportional to the product of their strengths.
B) is inversely proportional to the square of the distance between them.


This law is known as Coulomb's Law and can be expressed mathematically as

        Q1Q2
F∝ -------------
          d²

         Q1Q2
F=k------------
            d²

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What is Static Electricity (Electrostatics)



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What is Static Electricity (Electrostatics)

Static Electricity:-

Now, we will discuss the behaviour of static electricity and the laws governing it.In  fact, electrostatics is that branch of science which deals with the phenomena associated with electricity at rest.

Generally an atom is electrically neutral  i.e in a normal atom the aggregate of the  positive charge of protons is exactly equal to the -ve charges of electrons.

Attraction & repulsion

If,somehow, some electrons are removed from the atoms of a body, then it is left with a preponderance of positive charge. It is then said to be positively-charged. If. on the other hand,some electrons are added to it, negative charge out-balances the positive charge and the body is said to be negatively charged.

In brief, we can say that positive electrification of a body results from a deficiency of the electrons whereas negative electrification results from an excess of electrons.

 The total deficiency or excess of electrons in a body is known as its charge.


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What Is Capacitance or capacitor



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What Is Capacitance or capacitor

 Capacitance:-

The property of a capacitor to 'store electricity' may be called its capacitance.

As we may measure the capacity of a tank, not by the total mass or volume of water it can hold, but by the mass in kg of water required to raise its level by one metre, similarly, the capacitance of a capacitor is defined as "the amount of charge required to create a unit p.d. between its plates."

Suppose we give Q coulomb of charge to one of the two plate of capacitor and if a p.d. of V volts is established between the two,then its capacitance is

       Q
C=----------
       V

      Charge
=-----------------
          p.d

Parallel plate capacitor

Hence, capacitance is the charge required per unit potential difference.

By definition, the unit of capacitance is coulomb/volt which is also called  farad.


So, 1 Farad=1 Coulomb/volt


One Farad is defined as the capacitance of a capacitor which requires a charge of One coulomb to establish a p.d of one volt b/w its plates.

One farad is actually too large for practical purposes. Hence, much smaller units like microfarad,nano farad,micro-micro farad,pico farad are generally used.

1μF=10⁻⁶ F
1nF=10⁻⁹F
1μμF=10⁻¹²F

Incidentally, capacitance is that property of a capacitor which oppose any change of voltage accross it.




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Energy Stored In A Capacitor




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Capacitors In Series And Parallel in circuits

Capacitors in Series:-

With reference of figure,
   let C1, C2, C3 = Capacitances of three capacitors.
        V1, V2; V3 = p.ds. across three capacitors.
                       V  = applied voltage across combination.
                       C  = combined or equivalent or joining capacitance.
In series combination,charge on all capacitors is the same but p.d across each is diff.

                             
               V = V1+V2+V3


Or

Q/C=Q/C1+Q/C2+Q/C3
Or
1/C=1/C1+1/C2+1/C3


For a changing applied voltage          
   dV/dt =dV1/dt+dV2/dt+dV3/dt

We can also find values ofV1,V2 and V3,in terms of V.Now


Q=V1C1=V2C2=V3C3=VC

             C1C2C3
C= --------------------------
      C1C2+C2C3+C3C1


           C1C2C3
C= ---------------------
            ∑ C1C2


C1V1=CV
OR
V1=V•C/C1


              C2C3
V1=V---------------
             ∑C1C2



              C1C3
V2=V---------------
             ∑C1C2



              C2C1
V3=V---------------
             ∑C1C2

Capacitors in Series

Capacitors in parallel:-

In this case,p.d across each is the same but charge on each is different.....

Q=Q1+Q2+Q3

OR

CV=C1V+C2V+C3V

OR

C=C1+C2+C3


For such a combination,dv/dt is the same for all capacitors.

Capacitors in parallel

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Energy Stored In A Capacitor





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Insulation Resistance of a Cable Capacitor

Insulation Resistance of a Cable Capacitor-

 In a cable capacitor, useful current flows along the axis of the core but there is always present some leakage of current. This leakage is radial i.e. at right angles to the flow of resistance useful current.The resistance offered to this radial leakage of current is called insulation resistance of the cable.
             
                              If cable length is greater,then leakage is also greater. It means that more current will leak.
                             In other words, insulation resistance is decreased.Hence, we find that insulation resistance is inversely proportional to the cable length. This insulation resistance  is not to be confused with conductor resistance which is directly proportional to the cable length.

                            Consider i metre of a single-core cable of inner radius  r₁ and outer radius r2 (Fig.). Imagin an annular ring of radius ''r" and radial thickness 'dr'.

                          If resistivity of insulating material is ρ then resistance of this narrow ring is

                               ρ dr
                   dR = ⸻⸻
                              2πr × l

ஃ  Insulation resistance of l meter length of cable is

               r2      ρ dr                                                                   

∫dR =   ∫     ----------------       Or     
               ʳ¹      2πr l                                                                 
                       
        



              ρ                     r2
R =    ---------   |logₑr|
          2πr l                   ʳ¹


           

                ρ
  R =    ----------  logₑ(r2/r1)
               2πl

It Should be noted that-

(A)R is inversely proportional to the cable length.
(B) R depends upon the ratio r2/r1 and NOT on the thickness of insulator itself.


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Energy stored in a capacitor in #Hindi



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Energy Stored In A Capacitor

      The energy stored in a capacitor equals the work done to put the charge on the capacitor in opposition to the voltage on the capacitor.(एक संधारित्र में संग्रहीत ऊर्जा कैपेसिटर पर वोल्टेज के विरोध में संधारित्र पर चार्ज लगाने के लिए किए गए कार्यों के बराबर होती है)



                                             Electric Energy,W=½CV²     Joules
                                         

Energy Stored in a Capacitor:-

Charging of a capacitor always involves some ex- penditure of energy by the charging agency. This energy is stored up in the electrostatic field set up in the dielectric medium. On discharging the capacitor, the field collapses and the stored energy is released.
                          To begin with, when the capacitor is uncharged, little work is done in transferring charge from one plate to another. But further instalments of charge have to be carried against the repulsive force due to the charge already collected on the capacitor plates. Let us find the energy spent in charging a capacitor of capacitance C to a voltage V.
                   Suppose at any stage of charging, the p.d. across the plates is v. By definition, it is equal to the work done in shifting one coulomb from one plate to another. If 'dq'  is charge next transferred, the work done is  

एक संधारित्र में संग्रहीत ऊर्जा:-

 (एक संधारित्र के चार्जिंग में हमेशा चार्जिंग एजेंसी द्वारा ऊर्जा का कुछ व्यय शामिल होता है। यह ऊर्जा डायलेक-ट्राइक माध्यम में स्थापित इलेक्ट्रोस्टैटिक फ़ील्ड में संग्रहीत होती है। संधारित्र को निर्वहन करने पर, क्षेत्र घटता जाता है और संग्रहीत ऊर्जा जारी की जाती है।     
                           शुरू करने के लिए, जब संधारित्र को चार्ज किया जाता है, तो एक प्लेट से दूसरे प्लेट में चार्ज स्थानांतरित करने में थोड़ा काम किया जाता है। लेकिन संधारित्र प्लेटों पर पहले से एकत्र किए गए शुल्क के कारण प्रतिकूल बल के खिलाफ चार्ज की और किस्तों को ले जाना होगा। आइए हम वोल्टेज V को कैपेसिटेंस C के संधारित्र को चार्ज करने में खर्च की गई ऊर्जा पाएं।
                       मान लीजिए चार्ज करने के किसी भी चरण में, p.d  प्लेटों में v है। परिभाषा के अनुसार, यह एक प्लेट से दूसरे में एक coulomb स्थानांतरित करने में किए गए काम के बराबर है। यदि 'dq' चार्ज को ट्रांसफर किया गया है तो किया गया कार्य है)

   



                              dW=v.dq
Now,q= Cv       So,dq=C.dv          hence      dW=` Cv.dv


Total work done in giving V units of potential is
(विभव की V इकाइयों को देने में किए गए कुल कार्य हैं)
                     ᵥ                            ᵥ
          W= ∫Cv.dv= C|v²/2|
                   °                               °
         W=½CV²  =  ½QV  =  Q²/2C Joules

Where,C is in Farads and V in Volts.




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Capacitor types in hindi

There are many types of capacitors:-

Capacitor types & dielectrics

Although all capacitors work in essentially the same way, key differences in the construction of different capacitor types makes an enormous difference in their properties.

The main element of the capacitor that gives rise to the different properties of the different types of capacitor is the dielectric - the material between the two plates. Its dielectric constant will alter the level of capacitance that can be achieved within a certain volume.

Some types of capacitor may be polarised, i.e. they only tolerate voltages across them in one direction. Other capacitor types are non-polarised and can have voltages of either polarity across them.

Typically the different types of capacitor are named after the type of dielectric they contain. This gives a good indication of the general properties they will exhibit and for what circuit functions they can be used.

Overview of different capacitor types

There are many different types of capacitor that can be used - most of the major types are outlined below:

• Ceramic capacitor: 
• The ceramic capacitor is a type of capacitor that is used in many applications from audio to RF. Values range from a few picofarads to around 0.1 microfarads. Ceramic capacitor types are by far the most commonly used type of capacitor being cheap and reliable and their loss factor is particularly low although this is dependent on the exact dielectric in use. In view of their constructional properties, these capacitors are widely used both in leaded and surface mount formats.
• 
  

• Electrolytic capacitor:
• Electrolytic capacitors are a type of capacitor that is polarised. They are able to offer high capacitance values - typically above 1μF, and are most widely used for low frequency applications - power supplies, decoupling and audio coupling applications as they have a frequency limit if around 100 kHz. 
• 
  
• Tantalum capacitor:
•  Like electrolytic capacitors, tantalum capacitors are also polarised and offer a very high capacitance level for their volume. However this type of capacitor is very intolerant of being reverse biased, often exploding when placed under stress. This type of capacitor must also not be subject to high ripple currents or voltages above their working voltage. They are available in both leaded and surface mount formats.
• 
  
• Silver Mica Capacitor:
•  Silver mica capacitors are not as widely used these days, but they still offer very high levels of stability, low loss and accuracy where space is not an issue. They are primarily used for RF applications and and they are limited to maximum values of 1000 pF or so. 
• 
  
• Polystyrene Film Capacitor:   
• Polystyrene capacitors are a relatively cheap form of capacitor but offer a close tolerance capacitor where needed. They are tubular in shape resulting from the fact that the plate / dielectric sandwich is rolled together, but this adds inductance limiting their frequency response to a few hundred kHz. They are generally only available as leaded electronics components.
• 
  
• Polyester Film Capacitor:
• Polyester film capacitors are used where cost is a consideration as they do not offer a high tolerance. Many polyester film capacitors have a tolerance of 5% or 10%, which is adequate for many applications. They are generally only available as leaded electronics components. 
• Metallised Polyester Film Capacitor: 
• This type of capacitor is a essentially a form of polyester film capacitor where the polyester films themselves are metallised. The advantage of using this process is that because their electrodes are thin, the overall capacitor can be contained within a relatively small package. The metallised polyester film capacitors are generally only available as leaded electronics components.
• 
  
• Polycarbonate capacitor:
• The polycarbonate capacitors has been used in applications where reliability and performance are critical. The polycarbonate film is very stable and enables high tolerance capacitors to be made which will hold their capacitance value over time. In addition they have a low dissipation factor, and they remain stable over a wide temperature range, many being specified from -55°C to +125°C. However the manufacture of polycarbonate dielectric has ceased and their production is now very limited.
• 
  
• Polypropylene Capacitor: 
• The polypropylene capacitor is sometimes used when a higher tolerance type of capacitor is necessary than polyester capacitors offer. As the name implies, this capacitor uses a polypropylene film for the dielectric. One of the advantages of the capacitor is that there is very little change of capacitance with time and voltage applied. This type of capacitor is also used for low frequencies, with 100 kHz or so being the upper limit. They are generally only available as leaded electronics components. 
• 
  
• Glass capacitors:
• As the name implies, this capacitor type uses glass as the dielectric. Although expensive, these capacitors offer very high levels or performance in terms of extremely low loss, high RF current capability, no piezo-electric noise and other features making them ideal for many performance RF application.
• 
  
• Supercap: 
• Also known as a supercapacitor or ultracapacitor, as the name implies these capacitors have very large values of capacitance, of up to several thousand Farads. They find uses for providing a memory hold-up supply and also within automotive applications. 

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