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| Current Electricity |
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| One of the greatest discoveries of the eighteenth century was the discovery of electricity. Think of life today without electricity and you will realize the part electricity plays in our day to day life. |
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| Static charges will not heat a toaster or operate an electric fan. Most of the jobs we want electricity to do, require a continuous flow of electric charges. In other words, they require current electricity. Current electricity is the flow of charges. Electrons or negative charges move from where there are many to where there are fewer. In order to maintain the flow of electrons there must be a source and a way to carry them. |
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| You have learnt that the "coulomb" (C) is the unit for measuring charges. We consider electric current as the rate of flow of charge. When one coulomb of charge passes a given point in one second the corresponding current is one ampere (A). |
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| If the electric current is I (in amperes) then the amount of charge Q (in coulomb) which flows past a point in time t (in seconds) is given by |
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| Q = It (or I = Q/t). |
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| Note that although charge is carried by electrons which always pass from the negative to the positive terminals in a circuit, conventional current is always treated as flowing from positive to negative. |
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