Electricity and Magnetism are two of the most captivating topics of physics. That’s because you’ll find its laws and principles applied everywhere around us from nature to inventions. Particularly, after the discovery that Electricity and magnetism are inter-related, leading to the development of Electromagnetism, there have been radical changes in the world of physics, right from the invention of generators, electric motors, to using it to run trains that float on tracks and run at very high speeds. Being students, we surely ponder at times as to how these things work. Here, I discuss the fundamental laws governing the phenomenon of electromagnetism –
What is electromagnetism?
To your surprise the phenomenon of electromagnetism was discovered accidentally by Henry Oersted when he noted deflections in magnetic compass placed around a current carrying circuit. This was later confirmed by Faraday and this formed the rudiment for the modern scientists to work upon. Electromagnetism is defined as phenomenon of interaction between the electric and magnetic fields generated by charged particles. Let’s look at some laws which form the back of theory to field of physics.
Biot – Savart law:
This law quantifies the amount of magnetic field that is generated around an element when some current flows through it. This law helps us to find the amount of magnetic field generated around any conductor such as an infinitely long wire, solenoid, a circular coil, a cylinder or any other geometrical shape.
Lorentz force law:
When a magnetic field is created, a magnetic force acts on any object that lies inside that magnetic field. The magnitude of this magnetic force is given by Lorentz force law, which takes into account both the magnetic and electric force around an object. This is given by the equation –
This equation is particularly useful when analysing the phenomena occurring in outer space and also helps in the development of cyclotron (particle accelerators), electric motors, maglev trains, etc.
This is perhaps the most important of all the laws. Without this law, we wouldn’t have electric batteries, motors, transformers and other such devices. This law predicts how a magnetic field will interact with an electric circuit to produce an electromotive force (EMF)—a phenomenon called electromagnetic induction. Faraday proposed two laws – 1st law in simple words states that whenever a conductor cuts magnetic lines of forces, an emf is generated across its two ends. The 2nd law states that the emf induced is equal to the rate of change of flux in the coil i.e. how many times does the magnetic field associated around a conductor changes with time.
Ampere’s Law states that for any closed loop path, the sum of the length elements times the magnetic field in the direction of the length element is equal to the permeability times the electric current enclosed in the loop. This can be interpreted as another form of Biot-Savart’s law and is used for the same applications as the latter.
The aforementioned four laws are only a few of all the laws of electromagnetism but are the most fundamental ones due to the fact that these laws formed the basis for whatever is achieved so far in this field.
Considering from the exam point of view, especially JEE, electromagnetism is one topic which forms a major chunk of the questions and primarily most of the questions are formed to test you on your conceptual knowledge these four laws, so if you are a student wanting to pursue physics or engineering you would want to be thorough in these topics. Another topic in physics which is important is Archimedes Law check it out here.