Electrical Engineering ⇒ Topic : Introduction of Electrostatics
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April
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Electric charges are fundamental in nature. They are of two types and can be produced by friction.When a glass rod is rubbed with a silk cloth both the glass rod and the silk cloth attract pieces of paper. Also, there is a force of attraction between the glass rod and the silk cloth. The charge on the glass rod is taken as positive and that on the silk cloth is taken as negative. Suppose an amber rod is rubbed with cat's fur. The amber rod gets charged.When the amber rod touches two pieces of cork or two pith balls suspended by silk strings, the pith balls are repelled by the amber rod and they also repel each other. On the other hand, suppose one pith ball is brought into contact with a charged glass rod and the other pith ball is these brought into contact with the charged amber rod, and if these two pith balls are brought nearer to each other, they attract. This shows that there exists two kinds of electric chargesthat possessed by the amber rod, a negative charge and that possessed by the glass rod, a positive charge. The electrification of the glass rod when rubbed with silk cloth can be explained as being due to the migration of electrons from the glass rod to the silk cloth. This makes the glass rod positive and the silk cloth negative. Similarly, when the plastic rod is rubbed with fur, electrons migrate from the fur onto the amber rod making the rod negative and the fur positive. | |
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Member
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Introduction of electrostatics So far we have discussed that if two oppositely charged bodies are connected through a conductor,electrons will flow from the negative charge (excess of electrons) to the positive charge (deficiency of electrons). This directed flow of electrons is called electric current. The electric current will continue to flow so long as the 'excess' and 'deficiency' of electrons exist in the bodies. In other words, electric current will continue to flow so long as we maintain the potential difference between the bodies. The branch of engineering which deals with the flow of electrons (i. e. electric current) is called current electricity and is important in many ways. For example, it is the electric current by means of which electrical energy can be transfered from one point to another for utilisation. There can be another situation where charges (i.e. electrons) do not move but remain static or stationary on the bodies. Such a situation will arise when the charged bodies are separated by some insulating medium, disallowing the movement of electrons. This is called static electricity and the branch of engineering which deals with static electricity is called electrostatics. Although current electricity is of greater practical use, yet the importance of static electricity cannot be ignored. Many of the advancements made in the field of electricity owe their developments to the knowledge scientists obtained from electrostatics. The most useful outcomes of static electricity are the development of lightning rod and the capacitor. In this chapter, we shall confine our attention to the behaviour and applications of static electricity. | |
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