hi,

see generally when you start a particular module you have to start from the first chapters of that module, unless you face difficulty if you do not have the previous concept. for example like modern physics , this chapters has digital logic design and explanation of diode, transistor etc. with out the prior knowledge of other chapters you may start it. now coming to the chapter of electromagnetism you must have the knowledge of previous chapters current electricity, gauss laws etc.

hope you get the point.