Hi! I am using a beginners plane which has requirements of 500mAh and 7.4V 15C battery. Is it possible to use a 25C battery with the same current and voltage ratings?

yes but I think you will get less flight time wait and see what experts say

There is no problem in using a 25C battery of same specifiactions.You can use it with no problems.
 The C rating of a battery shows the max amps that can be delivered by the battery. So a 7.4v(2S) 500mah 15C can deliver 7.5A. And a 7.4v(2S) 500mah 25C can deliver 12.5A.

The only thing that you will have to take care about is the weight, the 25C battery will be slightly heavier than the 15C battery.
So yes nitesh is right you might get a lesser flying time only because the motor has to pull the heavier 25C capacity battery.

Yes you are right but one more issue.
in this case: lets assume 15c battery as 15c and 25c battery as 25c.
so when you divide 7.5 by 500 you will get 66.66 and when you divide 12.5 by 500 you will get so it is 66min and 40min.
it is because the 25c will give out more amps that means the battery will drain faster and on 15c it will give out less amps so that means the battery will drain slower.

But I am not sure as this may not be the case as the motor may take less amps and not taking the extra amps which will be stored in the battery itself.

Sorry for my bad explanation.

Please correct me if I am wrong

Let's get this straight. C rating DOES NOT imply the current will be drained faster as Nitesh said.
It is simply the maximum current that can "safely" pulled from the battery.
Eg: a 1000mah 10C battery can be used with a max current pull of 10000mah.
     While a 1000mah 25C battery can be used with a maximum current pull of 25000mah.

Yes the weight will be slightly higher, but it's not really that great.

The Current given out by the battery is never constant. It depends on the setup. If the setup needs 10000mah of current, the battery will supply that, "Regardless of Discharge Rate". It's always advisable to NOT exceed the max discharge rate of any given battery since it poses many hazards.

mAh is a unit of energy, not current

@sanjay ji yes. But what i think it implies is that a battery with a 1000mah rating will take 1 hour to discharge if a current of 1000ma is applied to it. And all my current pull should have been in ma instead. Sorry for the error

@nitesh yashodhanp is right. A battery 3S 1000mah 20C can supply 20A safely, but that doesnt mean that it is constantly supplying 20A its on the setup how much Amps it wants.