what exactly is "phase" ?

[ciitv]

i'm unable to get the concept of "phase". i come across this word in several contexts like phase response, cos(wt + phase), e(jwt). ......

Can somebody explain what phase is mathematically and physically. and how to accept it by intution . or reference to any website would be also helpful.

 

[shoivn]

Hi!
Give a check at Wiki.Hope it would help u!

http://en.wikipedia.org/wiki/Phase

Regards

 

[SkyHigh]

Phase is the angle with reference to 0 rad at the start of a cycle given by rad. 2Π rad is one full cycle of a period signal. When you have a phase shift, you have an angle in difference with respect to another signal or reference signal, for example, with respect to a clock or another input signal.
Sometimes we use degrees instead of rad, but bear in mind, most of the time, we use use rad for many scientific and engineering calculations.

 

[electronics_kumar]

' phase' is used as a reference to check whether the other one is leading or lagging...

 

[neils_arm_strong]

Phase gives the complete discription of an oscillating particle from th moment it started to oscillate.The Basic concept of phase can be understood easily if you study Simple Harmonic Motion(SHM) from any good physics text.

 

[mshareef]

1. Of a periodic, varying phenomenon, e.g., an electrical signal or electromagnetic wave, any distinguishable instantaneous state of the phenomenon, referred to a fixed reference or another periodic varying phenomenon.

Notes

1: Phase, i.e., phase time (frequently abbreviated simply to "phase" in colloquial usage), can be specified or expressed by time of occurrence relative to a specified reference.

2: The phase of a periodic phenomenon can also be expressed or specified by angular measure, with one period usually encompassing 360° (2Π radians).

3. That period of time during which a specified function occurs in a sequential list of functions.

4. The relationship between a signal and its horizontal axis, also called zero-crossing point.

 

[coolstuff]

the 'a' in (sin a) or (cos a) is called the phase of a sine function.it can be just a angle or in case of a physical oscillation,it can be a function of distance and time.

 

[priyankguddu]

Hmm Phase !!! Its a very intresting and vast topic!! Way of understanding may differ in many PHASE defination, but in turn they all means d same.
In a lay man's term u can say phase as "Delay" . Now going deep u can define phase as Delay from a particular refernce. Now if u consider a specific case of a periodic signal transmission as x(t)= Acos(w*t) , so if u have to receive the same signal ,u wud be expecting the same signal, but due to the transmission path x(t) got some delay and it wud not be same x(t) but x'(t)= Acos(w*t+ Delay(phase)). If the above explaination sounds u a bit convincing then reply me ,i'll post u my paper on PHASE.

 

[dedede]

i believe phase always link to the oscillation. u can imagine there is a ball are runing along with a circle. if u want to know the location of the ball, u must know the radius and angle. the radius can be compared to amplitude and the angle can be compared to phase.

 

[xischaune]

In case of a sinusoid, for example a sin wave, phase is the instantaneous slope...for example at the start of period, slope is 90 degrees and the value is sin 90 = 0

 

[Kral]

ciitv,
Phase or "phase shift" is a measure of the amount that one sinusoid leads or lags a reference sinusoid. It is commonly given in degrees or radians. These "units" are completley arbitrary. You can look at it as the fraction of a cycle by which one sinusoid leads or lags a reference. It is a dimensionless quantity. Degrees or Radians are simply dimensionless scale factors.
.
It is important to note that phase is not the same as delay. Delay has the unit of time (seconds, microsenconds, etc). Phase is dimensionless, although we attach the labels "degrees" or "radians" for convenience. It is awkward to say "A leads B by an amount equivalent to (37/360)ths of a cycle".
.
For example, a 1 Hz sinusoid has a period of 1 second. 45 degrees lag at this frequency represents a delay of 1 Second (45/360) = 0.125 seconds. A 10 Hz sinusoid has a period of 0.1 Seconds. A 45 degree lag at this frequency represents a delay of 0.1 second (45/360) = 0.0125 seconds. To convert phase to delay (or anticipation in the case of a lead), simply divide the phase by the frequency and multiply be the apporopriate scale factor (degrees/360 or radians/2*PI). This delay is called the "phase delay".
Regards,
Kral

 

[bangash]

phase is the reference of angle.initilally set to zero rad .

 

[bangash]

just consider it as angle.if not mentioned then by default considered as zero