What is Dipole Moment And Dipole Field?? Explained

Hello Everyone, Am Manjeet Singh and Today we will Discuss about Dipole Moment And Dipole Field... So Let's Start...

Dipole Moment: Dipole Moment (p) is a measure of the strength of electric dipole. It is a vector quantity whose magnitude is equal to protect of the magnitude of either charge and the distance between them.

i.e.      p=q(2a)     or      |p|=q(2a)

By convention, the direction of p is from negative to positive charge.
Then SI unit of dipole moment is coulomb-metre (C-m)
If charge q gets larger, and the distance 2a gets smaller and smaller, keeping the product |p|=q×2a=constant, we get what is called an ideal dipole or point dipole. Thus, an ideal dipole is the smallest dipole having almost no size.

Physical Significance of electric dipoles...
The study of electric dipoles is important for electrical phenomena in matter. Matter, as we know, consists of atoms or molecules which are electrically neutral. In a molecule, there are positively charged nuclei and negatively charged electrons. If the centre of mass of positive charges coincides with the centre of mass of negative charges, the molecule behaves as a non-polar molecule. On the contrary, if the centre of mass of positive charges does not coincide with the centre of mass of negative charges, the molecule behaves as a polar molecule and it possesses some intrinsic or permanent dipole moment. In the absence of an external electric field, the dipole moments of different molecules in a piece of matter are randomly oriented, so that net dipole moment of the piece is zero. When an external electric field is applied, the polar molecules tend to align themselves along the field and some net dipole moment developes. The piece of matter is said to have been polarised.

When non-polar molecules are subjected to the action of an external electric field, the centres of mass of positive and negative charges in the molecule get displaced in opposite directions. Thus, the external field induces some dipole moment in the molecule in the direction of the field. The induced dipole moments of different molecules in the sample add up vectorially to produce some net total dipole moment.

Dipole Field: The Dipole field is the electric field produced by an electric dipole. It is the space around the dipole in which the electric effect of the dipole can be experienced. The electric field of the pair of charge (-q and +q) at any point in space can be found from Coulomb's law and the superposition principal. To calculate dipole field intensity at any point, we imagine a unit positive charge held at that point. We calculate force on this charge due to each charge of the dipole and take vector sum of the two forces. This gives us dipole field intensity at that point. We shall show that though the total charge of electric dipole is zero, the field of the electric dipole is not zero. This is because the charge q and -q are separated by some distance. The electric fields due to these charges, when added, do not cancel out. However, at distances much larger than the separation of two charges, i.e., r>>2a, the fields due to q and -q largely cancel out. Therefore, at large distances from the dipole, the dipole field falls off more rapidly than like E~1/r² for a point charge.

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What is Origin Of Electric Charge In Electrostatics?? Explained

Hello Everyone, Am Manjeet Singh And Today we will Discuss About ORIGIN OF ELECTRIC CHARGE IN ELECTROSTATICS So Let's Start...

It is known that all matter is made up of atoms and molecules, the basic unit being an atom. We also know that every atom consists of a central core called the atomic nucleus, around which negatively charged electrons revolve in circular orbits. Every atom is electrically neutral, containing as many electrons as the number of protons in the nucleus. Thus, even though normally, the materials are electrically neutral, they do contain charges, but their charges are exactly balanced.

The vast amount of charge in an object is usually hidden as the object contains equal amounts of positive charge and negative charge. With such an equality or balance of charge, the object is said to be electrically neutral, i.e., it contains no net charge.

If the positive and negative charges are not in balance, then there is a net charge. Thus, an object is charged if it has a charge imbalance or some net charge. Hence, to electrify or charge a neutral body, we need to add or remove one kind of charge. When we say that a body is charged, we always refer to excess charge or deficit charge.

In solids, some of the electrons are less tightly bound in the atom. These are the charges, which are transferred from one body to the other.

When we rub two insulating substances against each other, we provide energy to overcome friction between them. This energy is used in removing elections from one substance and transferring them to the other. The transfer takes place from the material in which electrons are held less tightly to the material in which electrons are held more tightly, i.e., electrons are transferred from the material whose work function is lower to the material whose work function is higher. Consequently, the material which loses electrons acquires a positive charge and material which gains electrons acquires an equal negative charge. For example, when we rub a glass rod with silk, electrons are transferred from glass rod to silk. The glass rod becomes positively charged and silk acquires an equal negative charge. Thus, charging by rubbing is due to actual transfer of electrons.

The cause of charging is actual transfer of electrons from one material to the other. The insulating material with lower work function loses electrons and becomes positively charged and vice-versa.

Further, as an electron has a mass, howsoever small it may be, therefore there does occur some change in mass on charging. A positively charged body has lost some electrons and hence its mass reduces slightly. On the other hand , a negatively charged body has gained some electrons and hence its mass increases slightly.

Note that in rubbing, the no. of electrons that are transferred, is a very small fraction of the total no. of electrons in the material body. Hence, the charge acquired by friction is a very small fraction of the total positive and negative charge content of the body.

Further, as only the less tightly bound electrons in a material body can be transferred from it to another by rubbing, only under suitable conditions, we have to stick to certain pairs of materials to observe charging on rubbing the bodies.

In the Table, we have listed of objects which get charged on rubbing against each other. They have been divided into two classes, one acquiring positive charge and the other acquiring negative charge on rubbing.

Table: Objects Acquiring Two Kinds Of Charges On Rubbing

Positive Charge	Negative Charge
Glass Rod	Silk Cloth
Fur Or Woolen Cloth	Ebonite, Amber, etc.
Woolen Coat	Plastic Seat
Woolen Carpet	Rubber Shoes
Nylon or Acetate	Cloth
Dry Hair	Comb

Obviously, any two charged objects, in the same column repel each other and any two charged objects from different columns attract each other.

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What is Conductors, Insulators and Dielectrics??

Hello Everyone, My name is Manjeet Singh. Today we will Discuss about Conductors, Insulators and Dielectrics. So let's Start...

CONDUCTORS, INSULATORS AND DIELECTRICS

Most of the substance in nature are divided into two categories, namely, conductors and insulators.
A substance which can be used to carry or conduct electric charge from one place to the other is called a conductor. Silver is one of the best conductors. Other examples of conductors are copper, iron, aluminium, mercury, coal etc. Earth is a good conductor. Human body is also a good conductor of electricity. The liquid Conductors include, salt solutions, acids, alkalis etc.

In a metallic conductor, there are a large no. of free electrons which act as carries of charge. Infact, in a metal, the outer (valence) electrons part away from their atoms and are free to roam about in the body of the metal, but they cannot leave the metal under normal circumstance. The free electrons from a kind of electron gas, they collide with one another ; and also with the ions ; and move randomly in different directions. In an External electric field, the free elections drift against the direction of the field. The residual atoms made up of nuclei and the bound electrons remain held in their fixed positions. They constitute the bound charges in the conductor as they cannot move. In Electrolytic conductors, the charge carries are both, the positive and negative ions.

The insulators are the materials which cannot conduct electricity, i.e., they are poor conductors of electricity. Common examples of insulators are glass, rubber, plastic, ebonite, mica, wax, paper, wood etc. They are called insulators, because they prevent charge from going to places where it is not desired. Such substances possess a negligibly small number of free electrons.

Infact, in an insulator, each electron is attached or bound to a particular atom and is not free to move in the body of the insulator. As each electron stays near its 'parent' nucleus or within its atom or molecule, and cannot move far away from it, therefore, an insulator does not possess freely movable charges. Hence it fails to conduct electricity.

RETAIN IN MEMORY 
Insulators are also called Dielectrics. Obviously, dielectrics cannot conduct electricity. However, when an external electric field is applied, induced charges appear on the surface of the dielectric. Hence we may define dielectrics as the insulating materials which transmit electric effects without conducting.

When some charge is transferred to a conductor, it gets distributed readily over the entire surface of the conductor. In contrast, if some charge is put on an insulator, it stays at the same place.

A nylon or plastic comb gets electrified on combing dry hair or on rubbing. But a metallic rod does not get electrified on rubbing. This is because charges on metal leak through our body to the ground as both are good conductors of electricity.

When a charged body is brought in contact with the earth, all the excess charge on the body disappears by causing a momentary current to pass to the ground through our body. This process of sharing charges with the earth is called grounding or earthing. Earthing near the mains supply of a building is done by burying deep into earth, a thick metal plate. The electric wiring in our houses has three wires ; live, neutral and earth. The first two carry electric current from the power station and the third (earth) is connected to the buried metal plate. Metallic bodies of appliances like T.V., Frig., electric iron etc. are connected to earth wire. If a live wire were to touch the metallic body, charge flows to earth without damaging the appliance and without causing injury to us.

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