If you want to rank 1 in IIT JAM physics, then the thing you need to do is to complete the 90% of the syllabus atleast. Along with the concepts you need to do a lot of question practice from the classical books such as Spiggel Theoretical Mechanics, Girffiths Electrodynamics & Quantum Mechanics, Modern Physics from Arthur Beiser, Thermodynamics and Statistical Mechanics from Garg, Bansal, Ghosh etc. Practicing from this books will clear your conception and after that follow the previous year questions. Also it would be advisable for you to join a mock exam series online or offline as per your choice so that you get examination ready through out the way of preparation.
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I hope this helps. Wish you a great eve!