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__Fundamentals of Alternative Currents__

In this chapter, methods of finding R.M.S & Average
values of Alternating Voltages and currents are discussed with examples.

Note: Generation of Alternative currents and Alternative
voltages will not be discussed here.

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__Equations for alternative currents and voltages__

An Alternative voltage can be represented by,

E(t) = E

_{m }Sin wt
Where ‘E(t)’ is the Voltage at any instant, ‘E

_{m}’ is the Peak voltage.
Similarly an Alternative current can be represented by,

I(t) = I

_{m}Sin wt
Where ‘I(t)’ is the Current at any instant, ‘I

_{m}’ is the Peak Current.###
__Root Mean Squared (R.M.S) Value__

The average value of a Sine Wave (For a cycle) is zero.
Hence, Method of R.M.S is used.

Equation for the R.M.S voltage is,

Or in terms of phase,

Where, ‘v’ is the instantaneous voltage.

For a Sine Wave form,

It can be proved that the R.M.S of a Sine
wave is,

where v

_{m is the peak (or the maximum) value. }
You can use the above equation anywhere
(Only for Sine waves) without proving.

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__Average value__

Since the average value for a full cycle of a sine wave-form
is zero, we calculate the average value for a half cycle.

Or in terms of phase,

Where, ‘v’ is the instantaneous voltage.

All the other terms have their usual
meanings.

This is the End of the quick revision.
See you soon in the next article with solved examples.

Pabindu Lakshitha

B.Sc(Engineer)

Electrical and Information Engineering.

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