Alternating Current


INTRODUCTION: In the electrical circuits we have studied so far, the source of e.m.f. is a battery. The basic electrical component (or circuit element) is a resistor (an ohmic resistance) which controls the current in the circuit as per Ohm’s law. The direction of current in these circuits does not change with time. Such currents are called Direct Current (D.C.).

     But the electric energy that we use at home is of another form. It is called A.C. (Alternating Current). In fact, most of the electric power generated and used in the world is in the form of A.C.

ALTERNATING CURRENT: The magnitude of alternating current changes continuously with time and its direction gets reversed periodically.


     Electric current is of two types: D.C. and A.C.

     The voltage associated with Direct Current is called D.C. voltage, and, the voltage associated with Alternating Current is called Alternating Voltage (or colloquially A.C. voltage).

Question: Why is electric power distributed in the form of A.C. ?

Answer: There are mainly two reasons:

     (i) A.C. voltages can be easily and efficiently converted from a low value to a high value or vice versa using transformers.

     (ii) Using very high voltage (and so very low current) for transmission, A.C. can be transmitted from one place to another without much loss of energy.


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