# Sinusoidal Waveform Terminology - AC Circuits

### AC Circuits - Sinusoidal Waveform Terminology:

**Amplitude:**

The amplitude of sine wave is the maximum value (V/I) reached during a positive or negative alternation.

** Peak value:**

It denotes the maximum value of the alternative quantity reached during a positive or negative direction.

It is denoted as V_{m }, I_{m}

** Instantaneous value:**

The value of voltage or current at a particular instant (time) is known as instantaneous value.

Generally it is denoted by small alphabet(v for voltage and i for current).

** Cycle:**

One complete set of positive and negative values of an alternating quantity is called cycle.

ie during one cycle the wave from trace 0 to +max to 0 to -max to 0.

**Period:**

The time taken for one cycle is known as time period or periodic time.(T).

Its unit is time in seconds

**Frequency: **

No of cycles made in one second is called as frequency of the alternating quantity.

It is denoted by f.

The unit is Hertz or cycles/second

**Peak Value:**

The maximum value of an alternating quantity (It may be a current or voltage) during a cycle is called its peak value.

**Scalar quantity:**

A quantity which has only magnitude but no direction ( ex. Resistance)

**Vector quantity:**

A quantity which has both direction and magnitude (ex. Force)

**Phase: **

The development of an AC quantity through different stages as known as phase.

**In-Phase:**

When two alternating quantities reach their maximum and minimum simultaneously, then these quantities are called as in-phase.

**Out of Phase:**

When two alternating quantities do not attain their maximum and minimum values simultaneously then they are at out of phase. It is also known as Phase difference.

**Phase Angle:**

It is an angular displacement between two alternating quantities.

**Average Value: **

The arithmetical average of all the values of an alternating quantity over one cycle is called as average value.

For sine waveform

I_{Avg} = (2/π)I_{m} = 0.637I_{m}

**Root Mean Square (RMS) Value:**

The rms value of an alternating current is defined as that steady current which when flowing through a given resistance for a given time produces the same amount of heat as produced by the alternating current when flowing through the same resistance for the same time.

For sine waveform

V_{RMS} =(1√2)* V_{m} = 0.707V_{m}

I_{RMS} =(1√2)* I_{m} = 0.707I_{m }

**Peak Factor:**

It is defined as the ratio of the peak or maximum value, to the r.m.s. value, of a waveform.

For sine waveform = V_{m} /0.707V_{m } = 1/0.707 = 1.414

**Form Factor:**

It is defined as the ratio of the r.m.s. value to the average value.

Form Factor = RMS value / Average Value

For sine waveform = 0.707 / 0.637 = 1.11

Thanks for reading about basic terminology of sine wave...

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