Diagrams play an important role while learning a concept. May it be illustrative or schematic, diagrams are used as a tool for visualisation of a model while learning. NCERT uses this to its best to make learning effective for students. One should always keep in mind that exams have time constraint. Knowing when, where, and how to add diagrams in your answers is a must as these diagrams are essential to fetch good marks. It also helps the evaluator understand your answers without much effort.