Dear Nilesh,

Hope you are doing great,

It is determined by your knowledge and concepts on various chapters. If one covers the entire syllabus, he cannot guarantee a seat in IIT. If you did not study anything specifically for Jam 2018 and only took the mock test for JAM as previous year question then you may score average. However, you can easily cover mark scoring and other relatively simple topics. Thermal physics and mathematics, in my opinion, are relatively simple and take less time to cover than electronics, nuclear physics, and electrodynamics.

The following is the tips for the exam preparation:

https://university.careers360.com/articles/how-prepare-jam-physics

I hope this will help you,

Best of Luck :)