Electric Charge

© Jnana Prabodhini Educational Resource Centre

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Electric Charge


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We know Electric Bulb, Television which runs on electricity. The necessary electricity required for operating of these devices is brought through the electric wires , but since these devices are light weight, if there is any friction between them then electric charge gets develops in it. It is stable and remains where it has got generated and hence it is called static electric charge.


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When we wear nylon or polyster clothes, there is a friction between them and body, body hairs, at that time we get a slight electric spark. We get the same feeling when we try to sit on some plastic chair.


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When we run plastic comb or plastic scale on dry hairs, then electric charge develops on that scale. This electrically charged scale if taken near the small bits of papers, the pieces of papers get attracted towards that scale. The electrically charged object attracts the non-charged object towards it.


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Static Electric charge is of two types. a) Positive electric charge b) Negative electric chargeIf glass rod is rubbed on silk cloth, then positive electric charge gets developed on it. When ebonite, a plastic like rod is rubbed on woolen cloth, Negative electric charge gets developed on it.


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Two ebonite rods when rubbed on woolen cloth, negative electric charge gets develop on both of them. If both of these rods are brought near each other, they try to go away.Similarly , two glass rods positively charged when brought near each other, they try to be apart. This going apart is called as repulsion.


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But negatively charged ebonite rod and positively charged glass rod if brought near each other, they gets pulled towards each other. This is called as attraction. Hence it is observed that like charges that is between two similar charges, two positive or two negative charges there is repulsion. Different that is unlike, one positive and one negative charges attract each other.


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Every substance is made up of small particles called atoms. In every atom there is positive and negative charged small particle. They are equal in numbers and hence these charges do not have any effect on each other. Hence atom as such doesn’t have any charge on it.Every substance has different atomic structure and different atomic number, but still the positive and negative charges on the atom in it neutralises each other and hence normally there is no electric charge on the substance.


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When Ebonite rod and woolen cloth, Silk cloth and glass rod are rubbed against each other, some negative particles pass from one substance to another. Negative particles from glass rod settles on silk cloth. Negative particles from Woolen cloth passes on ebonite rod, and hence glass rod gets positive charge and ebonite rod gets negative charge.


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The Negative particles which pass from one substance to another substance are called electrons. Positively charged particles are called Proton.If positively charged substance is brought near a neutral/ uncharged substance, negative charges in the neutral substance gets attracted towards positive charged substance. At that time positive charges are repelled. Because of this the tip of the neutral substance which is near the positively charged substance, negative charges gather near that end. And positive charges remain at the other end.


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In this way, tip of the positively charged substance has unlike whereas other end has like charges. One charged and other uncharged object if brought near each other , then charge gets develop on the uncharged object. Electric charges developed in this way is called electrical induction.


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The object initially uncharged and then charged because of induced charges, when moved away from charged body , the particles will come back to original position. At this moment no charges exists on the object. It means that an induced charge exists only so long as the charged body is placed nearby.


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The electroscope is a simple device to identify electric charge. In electroscope a metal disc or ball is attached to one end of a copper or aluminum rod. To the other end are attached two thin metal leaves. This rod is fitted in a one holed cork stopper and the stopper is fitted on a conical flask in such a way that the metal leaves will be inside the flask and the disc, outside.


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Sometimes, to make the electroscope more sensitive, gold leaves are attached to the end inside the flask.The moving apart of the leaves of the electroscope is the test for finding out if the body is charged.


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If a body with no charge is made to touch the disc of the electroscope the leaves at the other end remain closed. But, if a positively or negatively charged body is brought in contact with the disc, then like charges develop on the leaves and they repel each other and fly apart..When charged body is taken away from the disc, the positive or negative charged particles regains it’s original position. Leaves comes back to it’s original position i.e near each other.


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If positively charged object is brought near the disc, then negative particles on the rod gets attracted towards it.Because of this at the other end of the rod positive charged particles remains. Since they are like charges, they repel each other and hence leaves fly apart. When charged object is taken away from the disc, negative particles occupies their original position , leaves comes near each other. In induction negative charged particles can move away from their original position but positive charged particles doesn’t move from it’s original position.


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During rains when lightning strikes there is danger to tall buildings. To prevent any damage due to lightning, a lightning conductor is fitted at the top of the building. A lightning conductor has a pointed shape and is made of copper. A thick strip of copper is attached to it. The other end of this strip is buried directly in the ground. When lightning occurs it is attracted to the pointed lightning conductor and from there flows directly into the ground. Thus any damage to the building due to lightning is prevented.

Electric Charge

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Transcript of Electric Charge