# 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 the average value is

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 the root mean square(RMS) value is

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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