How to identify ragas in carnatic music?

[ts]

It depends on the scope of the ragam. As RR Pointed out, the scope of Nadaramakriya is limited and hence an elaborate alapana would not be possible without any repeats. Also there are swarams that the performer can have as a base (nyasa) and render. These limit the scope of the ragam and hence one hears the same "pidi" in almost all renditions.

For example, you cannot hear someone renderring Sankarabharanam from the Ni, dha and ma swarams. Eventhough these are swaras allowed in Sankarabharanam, the alapana at no point will stop at them and elaborations will not be done on them . On the other hand, for kalyani, traversing and basing these swarams for alapana is allowed. Hope i am making it clear and that this helps.