When you compress air it heats up and requires increasing amounts of energy to continue compressing it. A two-stage compressor with intercooler will cool down the heated air, thus requiring less energy to compress it to higher pressures.
Really, you should refer to your physics textbook instead of simply posting questions here. Turn to the section on gas laws. For one thing, doing your own research will turn up lots of valuable information that would help you in your studies and future career. For another, I've been known to sometimes deliberately post wrong answers here to teach wannabe homework cheats valuable lessons in honesty. There, now you're likely to have doubts about the reliability of my clarification.
Oh, and I doubt it would kill you to use proper grammar and punctuation to make yourself more readily understood.
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If only you knew the power of the Dark Side of the Force
This is not being a home work cheat as you expressed it, I did some research but I could not find satisfactory answers so I want you to reinforce my research not calling me a cheat.
Most of the explanations are not exact, hope this will clarify my position to you.
My apologies. You should have made it clear because we get a lot of homework cheats asking such similar questions here. And for the record, the information I gave you is correct.
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If only you knew the power of the Dark Side of the Force