In this chapter we would learn how voltage and current changing with time are related to each other in various circuits with components namely resistors , capacitor and inductor .
Alternating current on the other hand is produced by voltage source whose terminal polarity keeps alternating with time i . e . terminal which was positive at one instant of time becomes negative some time later and vice – versa . Due to changing polarity of voltage source direction of flow of current also keep changing .
Alternating current and Alternating EMF
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An alternating current is one whose magnitude changes sinusoidal with time . Thus alternating current is given by
Where i 0 = current amplitude or peak value of alternating current If T is the time period of alternating current and f is the frequency , then
Where ω is called angular frequency of A . C and φ is known as phase constant
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Instead of sine function AC can also be represented by cosine function and both representation leads to same results . We will discuss circuits with sine representation of A . C
Figure below shows the variation of A . C with time