why is that cyclopentanone oxime have 5 different c peaks
Simply put, there are 5 different carbons in the molecule. Consider replacing each of them in turn with silicon or some phantom element (assume same valency etc) and you will see that there are 5 different molecules formed.
C
2 and C
3 are different as are C
4 and C
5, consider the rotation of the C=N bond.