The CSIR trends over the recent years on this topic, are relatively easy to moderate questions in terms of difficulty. They require a crystal-clear understanding of concepts, a thorough knowledge of basic formulae, even the sign accompany a term in the equation can be reversed in different options confusing the student. Another pattern seen is that the question may look elaborate and lengthy, so we perceive it as tough, but it may just take a clever application of simple equations to crack it.