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