This is the first video in sparkphy. Well what is a magnetic field, here this invisible field which moves a magnet. All the physics enthusiasts , you guys know what is a magnetic field and what it does. But where does the magnetic force come from. Electric charge creates electric force but magnetic force is not created by magnetic charge. That’s also is produced by electric charge but when it’s moving which is nothing but an electric current. So how does the electric current creates magnetic force? Let’s dive into space time to find how this works. Let’s take a line of charges extending to infinity, now the electric field is away from the line. And the electric field is inversely proportional to the square distance. Now imagine the frame that we set earlier is moving. Here comes the fancy part and the concept which I fancy so much, theory of relativity which states that the faster you travel in time the slower you travel in space so whenever the frame starts moving there comes time dilation and length contraction. Now here the as the length contracts frame moves which increase the electric field but the charge is same and there is no vertical disposition of the charges but still the electric field increases this pseudo increase in the electric field is nothing but the magnetic field. Viola