How Important are Electromagnetic Induction and Alternating Current for JEE Mains?

JEE Main is one of the main examinations in India for aspirants in the field of Engineering. It is an important entrance examination for without it, students who want to pursue the Engineering field in top institutes of the country like IITs, NITs, and other government colleges cannot do so. Hence, students need to prepare for JEE Main in order to compete in getting a seat in these institutes and colleges. The examination is generally conducted by the National Testing Agency (NTA) and students securing good marks can pursue the engineering courses they want in some of the best Engineering institutes present in the country.

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For cracking this examination, the students need to put in a lot of effort and dedication. This examination is not easy, and the students need to know the ins and outs of this particular entrance examination so that they will have an idea of how to go about the preparation step as smart preparation with a proper timetable is a must. On top of that, the students must be sincere and consistent in their preparation. The main paper for the JEE entrance examination includes three main subjects namely Physics, Chemistry, and Mathematics. Apart from these, the other two are the English and Aptitude test. Among these the most challenging one for many students, although all the three need daily studying and practicing as they are not easy but JEE Main Physics is the most challenging section as the students need to have a clear understanding of the concepts, derivations, theories, etc., in order to tackle any question that comes during the examination, most importantly in solving the numerical.


Most of the students find it very difficult in scoring high marks or good grades in Physics as they have not mastered the preparation technique for this particular subject. So, in order for the students to master the JEE Physics, they need to know how questions come from this subject, make a proper timetable for studying, use guide books and reference books for help. Most importantly the students must be clear with the concepts of different topics under various chapters that are in the JEE Physics syllabus. Students can also opt for good coaching classes online or offline and can download many free PDF of JEE Main of different topics that can help in their preparation.


There are 25 questions that are included in the JEE Physics Main paper that carry 4 marks each. Physics for  JEE Main syllabus is vast and includes chapters from both Class 11 Physics and Class 12. To score in JEE Main examination, the students must be thorough with the topics as the paper does not follow generally follow a trend in setting particular types of topics. Basically, the students need to be prepared with almost all the chapters included in the syllabus.

The Electromagnetic Induction and Alternating Currents are chapters that are also included in the Physics syllabus for JEE Main. If the students want to get good marks and to score at the most 50-60%, these chapters must be included in their topics to study.


Some important Points to Remember:

  1. Electromotive Induction formula

e = N x


e  is induced voltage (volts)

N: the number of turns in the coil

Φ is the magnetic flux ( Weber)

t is the time (seconds)

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  1. Self Induction

Self Induction is defined as a phenomenon where a change in the flow of current through the coil produces an emf in the same coil. At any instant, when current flows through the coil, the magnetic flux is directly proportional to the current that flows through the circuit.

Magnetic flux is given by Φ = LI


L = Self Inductance

Let e be the emf that is induced in the coil then, it can be written as:

e = dΦ/dt

e = d(LI)/dt

Thus, e = L(dI/dt)

  1. Mutual Induction

Mutual Induction on the other hand is the phenomenon where a change in the flow of current in the primary coil produces emf in the secondary coil. The emf that is produced in the secondary coil is directly proportional to dI/dt in the primary coil.

Alternating current is a current that at regular intervals of time changes its magnitude and polarity. The time period is the time interval between two successive cycles and the term frequency is used for the number of cycles or periods per second. The amplitude is the maximum displacement of the wave.

AC can actually be produced by various methods, one of which is by using a basic single coil AC generator that consists of two-pole magnets with a wire having a rectangular shape. Here, mechanical energy gets converted into electrical energy.

Students can download previous years question papers online as well as solved examples which can help them in their preparation process.

Can you solve the question: The instantananeous current from an a .c. is I = 10 sin 314 t. What is the frequency of the source and virtual value of current?

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