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Electricity and Magnetism usually has the highest weightage in Physics papers across many exams. It is a vast topic and quite diverse as well. A lot of skills are required to be good at this topic. In this article I have tried to pen down some tips that will help you achieve mastery in Electricity and Magnetism.

Tips to master Electricity and Magnetism :

Make proper use of Kirchoff’s Laws:

Kirchoff’s current law and Kirchoff’s voltage law are the two fundamental laws used for solving current electricity systems. They are essentially charge and energy conservation laws. It can also be a bit confusing to use these laws. When there are multiple paths involved then there may often be a repetition of equations. When you have applied the conservation laws for two smaller paths and are then applying the law for a path which is the combination of the two aforementioned paths then you won’t get a new equation but instead just a linear combination of the two previous equations. This makes sense because an equation cannot appear out of nowhere, there must be some physical significance behind it (in this case the conservation of charge/energy). So if you have already applied the conservation law for a given path indirectly by a combination of two smaller paths you cannot expect a new equation. So be careful while applying Kirchoff’s laws.

Getting the direction right:

It can often be very confusing getting the direction correct in complicated systems in both electricity and magnetism. One can have a hard time guessing the direction of current and it can get really confusing to apply conservation laws in such cases. There is a simple hack to avoid all this. Simply assume an arbitrary magnitude and direction for the current and solve the question. If your assumed direction is incorrect then the answer will simply turn out negative. In that case the actual current will be in the direction opposite to which you have assumed with the same magnitude. This is a simple trick which can avoid a lot of confusion.

Try to get a perspective from Energy Conservation:

Energy Conservation is one of the most useful tools in physical analysis. One should try and understand electrical systems from an Energy perspective. This will be of great help in very complicated systems. Know how energy is dissipated or stored in various electrical components like a resistor or a capacitor. This will help in generating equations and getting boundary conditions as well. You can also use it as a means to cross check your answer. If it violates energy conservation it cannot be correct. It also gives an insight into what is really happening in the system and that can be helpful in answering qualitative questions that JEE Advanced asks.

Understand Things at a Microscopic Level:

 In electrical systems it is very useful to understand how things are working at the microscopic level. How a steady electrical current is set up in case of current electricity or how a particular charge distribution is achieved in static electricity. You should try to get a picture of what is happening. Of course, strictly speaking there is no definite theory which completely explains all of current electricity but that is beyond the scope of college level examinations. Here, having a brief idea of what is happening suffices.

Uniqueness Theorems:

This is a bit beyond the JEE syllabus however it is a very useful tool in Electrostatics. The uniqueness theorem states that given a charge distribution in a region and boundary conditions (i.e. values of potential at the boundaries) there exists a unique solution to the potential in that region. That implies that there exists a unique induced charge distribution producing the potential in that given region. In simple words, if you can find an induced charge distribution that satisfies the value of potential at the boundaries without disturbing the original charge distribution then that is the induced charge distribution. So in a question involving conductors with some charges placed at some points, if you are able to find an induced charge distribution that gives zero potential on the conductor and at a large distance from the charges then it is the induced charge distribution. I would suggest you go through some examples of this technique to properly understand it. I would also suggest that you use this only when you have no other method to solve the question as you don’t know the equation in its exact form. So there is a chance you might make a conceptual mistake.

Understand the concept of induced EMF properly:

This concept is one of the most confusing in whole of E&M. It is very difficult to understand the concept of induced EMF intuitively and there is no good intuitive understanding as such. It is just a fundamental law of electromagnetism that has been observed. You cannot really go to the microscopic level and try to get a picture of why change in magnetic flux produces an electric field. Another thing that is confusing is the minus sign in Lenz’s law. How to determine the direction of induced EMF and what does the minus sign signify? The convention is as follows – you assume a direction of induced EMF and curl the fingers of your right hand in that direction. The direction of your thumb will give you the direction in which you must calculate magnetic flux and hence change in magnetic flux. The induced EMF in the direction of your fingers will then be the negative of the rate of change of magnetic flux in the direction of your thumb. Be careful about this.

Practice a lot in Magnetics:

Magnetics is all about understanding a few basic laws and then using integration to find out the magnetic field produced by a current distribution. All questions will require you to use Biot-Savart’s Law or Ampere’s Law and then calculate the magnetic field. The tricky part will be deciding how to tackle the problem for the given current distribution. That is a skill you will learn by practice. As you encounter different current distribution you will learn different ways and tricks to do the integration and go about solving the problem. So practice a lot in this section.

Electricity and Magnetism has the highest weightage in most examinations and it is not very difficult either. You should be conceptually very strong in electricity and magnetism.

One of the best books to study electricity and magnetism is ‘Concepts of Physics’ by Dr.H.C. Verma. Hear it out from the man himself about how to read the book ‘Concepts of Physics’.

You may also like to know about tips and tricks to master sound in JEE.

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