Electromagnetism forms the major part of the class 12th syllabus and is one of the highly weighted sections for JEE Physics. This entire module requires a lot of practice, intuition and problem solving skills. The mechanics portion learnt in class 11th acts as tool to solve the problems of electromagnetism (Yes! You are going to need it! Quite a lot from sections: energy conservation, momentum conservation and Newton’s laws of motion).
Let’s go chapter wise to make things simpler:
• Electrostatics: Electrostatics begins with Coulomb’s law, principle of superposition and then goes on to the concept of electric field, electrostatic potential and other ideas that form the basis of electromagnetism. These are the fundamental concepts and the students are advised to get a thorough understanding of these topics. Sufficient practice is required for all of these topics. In JEE, simple questions are asked from this topic which can be cracked easily, if one has refined concepts. An important portion of electrostatics is the concept of “conductors in electrostatics”. Most questions in electrostatics are based on the properties of conductors under electrostatic condition. So, it is recommended that students should practice ample of questions from this topic. Another extremely important idea is the idea of electrostatic flux and Gauss’s law. Both of these ideas are highly important and if one can correlate them with other topics, they can be very useful to solve completely unrelated problems. Usually, there is always a question in JEE which ultimately involves calculation of flux of a charge through some or the other surface.
• Capacitors: This chapter is another simple but important part of JEE syllabus. It is basically the application part of electrostatics. Those who have covered electrostatics well would find this chapter a cakewalk. Some new concepts taught in this chapter are very interesting and easy to understand. This chapter is important from the point of view of Olympiads as well. The idea of dielectrics is also introduced with this chapter and a number of questions are asked in JEE which require you to calculate energy stored in capacitor / electric field by capacitor, etc. – all involving concept of dielectrics. In fact, an entire question in INPhO 2013 was based on a capacitor with a dielectric whose dielectric constant varied as a function of position.
• Current electricity: Ohm’s law and Kirchoff’s law form the key framework of this chapter. It’s one of the easiest chapters in JEE syllabus and it takes only a little effort to master it. However, the chapter has fairly good weightage in JEE and so it is recommended that students practice a large number of questions from this chapter so as to avoid silly mistakes in the exam. RC circuits are very important from the point of JEE. One should keep the “mechanical analogy” in mind while solving the problems of RC circuits. Sometimes, a tough RC circuit problem can be solved within a minute if one is able to figure the appropriate mechanical analogy. Another important concept is “heating effect of electric current”. This concept combined with the ideas of thermodynamics may be used to form some of the best mind bending questions.
• Magnetism: This chapter involves numerous applications of the mechanics portion learnt in class 11th. Good questions are framed under the concept of a particle in an electric as well as magnetic field. And one should be thorough with various concepts of mechanics to be able to solve the problems, particularly, basic kinematics, work energy theorem (+ the idea that magnetic field doesn’t do any work), law of conservation of linear momentum, etc. Most questions are asked from calculation of magnetic field in various cases. Another important “centre” of questions is – Magnetic moment. It has been observed that there are a few questions in JEE from magnetic moment, every year. So, it is recommended that students practice enough questions involving calculation of magnetic moment and related applications like – basic idea of magnetic materials and the explanation using the concept of magnetic moment. A loop in a uniform magnetic field is also an important topic of discussion. Several questions are asked from this. Some good problems are also derived from the concept of “moving coil galvanometer”. So, boot yourselves up and get ready to see a few new questions in JEE from magnetism as well.
To conclude, Electromagnetism forms a big portion of JEE syllabus and if practiced properly, it may help you change your rank completely. But, at the same time, Electromagnetism needs a lot of practice and patience to master. Initially, one may find it boring/ difficult to understand for whatever reasons, but it becomes very easy (and fun too!) if ample no. of questions are practiced from the prescribed textbooks/ study material.
Recommended books: DC Pandey, HC Verma, NCERT, Resnick Halliday