The magnetic field is generally interpreted as a region where the force of magnetism acts. This force of magnetism is generally produced as a result of moving charges or some magnetic material. The origin of this interpretation dates back to the 19th century. During the early years of the 19th century, a scientist named H. C. Oersted discovered that a current-carrying conductor produces a magnetic effect around it. Although science and technology were not as developed as they are today, based on observations, it was already known that the effect of lightning, striking a ship caused the malfunctioning of compass needles, disrupting the navigation system. People then knew that lightning was a form of electricity and also the fact that the working of a compass is based on the earth’s magnetic field. This suggested a relationship between the two, the moving electric charge (current) and the magnetic field.
Current is generally defined as the rate of flow of charge. We already know that stationary charges produce an electric field that is proportional to the magnitude of the charge. The same principle can be applied here, moving charges produce magnetic fields that are proportional to the current, and hence a current-carrying conductor produces a magnetic effect around it. This magnetic field is generally attributed to the sub-atomic particles in the conductor, for e.g. the moving electrons in the atomic orbitals.
The magnetic field has both magnitude and direction. Hence it is a vector quantity and is denoted by B (in the diagram given below). Magnetic field due to a current-carrying conductor depends on the current in the conductor and the distance of the point from the conductor. The direction of the magnetic field is perpendicular to the wire. If you wrap your right hand’s fingers around the wire with your thumb pointing in the direction of the current, then the direction in which the fingers would curl will give the direction of the magnetic field. This will be clearer with the diagram shown below where the red lines represent the magnetic field lines.
The magnetic field produced due to a current-carrying conductor has the following characteristics:
It’s difficult to comprehend the role of magnetism in our lives as we can’t see them. Take a look around and the realization of its importance will not be as difficult. The motors that are used so extensively around the world whether it’s a toy car or a bullet train or an aircraft or a spaceship they all use the same magnetic effect.