Why Only +15/-15 Volts Applied to Op-Amp 741? What is the Reason Behind This?

Maybe the specification means anything between -15 and +15 volts?

First, shame on you. Look up the data sheet for the part and you will see the minimum and maximum ratings for the part. You have to do your homework here as part of the design process.

That voltage is probably a typical rating, but can be operated below that point. There will also be examples circuits in the data sheet that will guide you with operational applications.

First, Shame on my Faculty person who asked me that type question that i mentioned here. I agree with you "HERO".I also know that due to applied differential input voltage and in saturation it's output voltage becomes change within one volt of +Vcc and 2v of -VEE supply. due to split power supply can change +14Volt in positive and -13V in negative, that calls positive-negative saturation voltage respectively...but please can you describe here with this kind of reason...?

Some thoughts:

There is an analysis program for the PC called LTSpice. It is available for free as a download from Linear Technology. You can model the circuit on your PC to observe the behavior. The software is very accurate and relatively easy to use.

You might also check for a book or books on Op-Amps to understand how they work if needed.

I am not sure that I fully understand your question. If the amp circuit is correctly designed the output should be consistent with respect to the input. That is, for supply voltages of less than ±15VDC the maximum input voltage can be equal to the supply voltage and the output should be respectively balanced.

If you supply voltage is ±15 VDC the maximum output should be typically be ±14 VDC. If not, then you have something wrong with the circuit or offset null circuit.

Put really simply, the 741 is an op amp which is an operational amplifier which is designed to amplify both AC or DC (or a combination of both) signals. The op amp needs (generally) to have a positive and negative power supply to allow it to amplify said AC signal using a 0V reference (hence the data sheet +/- voltage levels).

Yes you can operate the op amp using +12V referenced to a 0V rail (ie- a DC supply) to amplify DC, but if you try and amplify an ac signal referenced to 0V then you will get the positive half of the waveform but wont get the negative half (unless you offset the reference voltage above 0V).

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The data sheet is simply indicating maximum operating voltage levels either +/- for AC or + (referenced to 0V) for DC.

Actually, if you must know, it all started with the practical limitations of the transistor manufacturing technology at the time the Op-Amp was first introduced. Since then, there have been many more technologies introduced. And if you needed one with more voltage or power you just built it out of selected discrete components.

The real advantage was having an amplifier on a chip. You might not realize how many people were willing to celebrate that innovation just because of how many applications were solved by the invention.

Yes, you can run most of them at lower voltages but you must leave a little room for internal power consumption. If you operate with a +15 and -15 voltage supply, your useful range for the output can not exceed the "rail to rail" voltage. In this case, that would be about +14 volts to -14 volts. Often you will find that what works on paper rarely takes into account the full realization of the design. If you can't get the design to work within the range you need, you may have to do some real hard core engineering. Good luck with that! Temperature and frequency compensation is frequently a challenging problem.

The +15 and -15 voltages are there for maximum voltage swing i.e. 30V...

If you were to use say a +15V rail to 0V (Ground), you have only a 15V swing...

Split rail supplies are mostly used in amplifiers and pre-amps...