Why Sine Wave

Hello, Every one i just want know why we use only sine wave for our A.C circuits???

what are the reasons behind it????

Well, at the most basic level, it's because that's the way it's made! An electrical generator is a huge magnetic machine which induces currents, and being circular (360 degrees), that's the "shape" the electricity comes out.

For the more complex explanation...

http://en.wikipedia.org/wiki/Alternating_current#Mathematics_of_AC_voltages

can we say when we make fourier transform of our sine wave then this wave shape having less number of harmonic components?????

Yes Asad, you are right to an extent, sine & cosine waves are the most basic waveforms to study.
It is easy to integrate, differentiate in short you can work upon such kind of wave. If you take up square wave which is also made up of sine wave & harmonics, so studying sine wave forms the basis.

It's how nature works. The natural outcome of an armature turning at a constant rotational velocity in a constant magnetic field is a sinewave.

http://youtu.be/ynZmZzOhBkM

A sine (or cosine) wave has no harmonics. Also, each harmonic of a "distorted" waveform is a sinewave (or cosine -- sine or cosine is relative).

In AC ,the flow of electric charge changes periodically (
i.e in +ve cycle & -ve cycle)

It is the wave form produced in the least expensive form of a rotating armature in a constant magnetic field. Pulsating DC (simply on and off) through a transformer produces a pseudo sine wave, and a modified PWM (Pulse Wave Modulator) - stepped - produces a modified sine wave closer to a mechanically produced sine wave. A modified PWM is what most power inverters use to convert 12V DC battery to 120V AC for appliances.

It simply is how the alternating current wave form is produced in an alternator (AC generator with slip rings). The RMS (Root Mean Square) power is 0.707% of peak, or peak is 1.414% of RMS. 120VAC RMS is 169.68V AC peak @ 60 CPS/Hz.

The sine wave form is not a specifically 'targeted' wave form, it is the 'result of' mechanical rotation through a magnetic field.

Through a PWM, there can be a square wave form or stepped wave form. Since the sine wave that is naturally produced in an alternator is the most cost effective, the classic sine wave is what is most commonly used.

Hi

There are many references to this on the net

The main reason we use a sine wave in ac circuits is due to the behaviour of a generator which generates alternating current

If you plot voltage output from a generator according to time you will derive a graph which is sinusoidal in shape and has a direct relation with degrees and radians making up a complete circle.

Or one cycle or 360 degrees or 2 pi radians the units of angular measurement


For a better and more complete understanding of the subject refer to this link below

http://www.allaboutcircuits.com/vol_2/chpt_1/2.html

Or

If. You use google or a similar search engine which takes a little practice

Can be a little challenging at times would you believe there are some more thorough explanations to this subject as well


I also suggest further studies in mathematics which if you google again, does mean a little bit of effort, You can gain more understanding by looking up the following

The vertical and horizontal projections of a rotating line

The measurement of Angles in degrees

The definition of the Six Tigonometric Functions

Graphical Representation of the properties of the function Y = Sin (pheta )


or

if you can manage to download a file please see link below

If we rotate any thing through 360 degrees, it produces sine wave against time and radius of the rotating device. Radius gives amplitude of the sine wave and time required to rotate wheel for one rotation gives frequency.

To see sine wave; just mark a point on bicycle tyre and mark the place touching the wheel on ground. Move bicycle and trace the movement of mark on tyre for one complete rotation; you will get a sine wave. Similarly when any dynamo or generator armature rotates it traces sine wave.

Thus armature coil continuously rotates in magnetic field producing EMF similar to sine wave. number of rotation per second gives frequency of sine wave in Hertz. Thus all AC voltages currents are sine waves.

AC is generated at lowest price and it is available on wall socket.

AC do not have any harmonic frequencies so it do not produce any noise in device when used.

Greetings, all explanations are good info. I just would like to add a simple bit of info for the non as well educated persons. The sine wave is a result of the rotating magnetic interaction when the magnets (which, remember, have polarity as in north and south or if you wish plus and minus)rotate past the separate coils in the generator. As the rotating magnetic field turns, both the attracting and the repelling polarity of the magnets pass the coils at opposing times. This rise and fall, or attraction and repulsion, with neutral or 0 in the center of the two that creates a sine wave as the potential rises and then falls 60 times a second in the USA and 50 times in the UK. As the magnets approach and pass then move away and the next magnet approaches and rises then passes and so on that creates the wave as voltage rises to peak and falls to 0 on to the minus peak as the magnet passes and rises back past 0 to the positive peak. Hence the name alternating current. It alternates between the positve and negative polarities in direct ratio to the magnetic field reversing polarity. (Magnet polarity- lay 2 end to end they will either attract or repel each other, flip and they will behave opposite)