Magnetic Field due to a Current-Carrying Conductor

Magnetic Field due to a Current-Carrying Conductor
A Magnetic field is generally interpreted as a region where the force of magnetism acts. This force of magnetism is generally produced due to a moving charge or 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 and 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.

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Magnetic Field Due to Current Carrying Conductor
Current is generally defined as the rate of flow of charge. We already know that stationary charges produce an electric field proportional to the charge’s magnitude. The same principle can be applied here. Moving charges produce magnetic fields which 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.
A magnetic field has both magnitude and direction. Hence, it is a vector quantity denoted by B (in the diagram below). The magnetic field due to a current-carrying conductor depends on the conductor’s current and the distance from the point. 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 below, where the red lines represent the magnetic field lines.

Characteristics of Magnetic Field Due to Current Carrying Conductor
The magnetic field produced due to a current-carrying conductor has the following characteristics:
It encircles the conductor. It lies in a plane perpendicular to the conductor. Reversal in the current flow direction reverses the field’s direction. Strength of the field is directly proportional to the magnitude of the current. Strength of the field at any point is inversely proportional to the distance of the point from the wire. It’s difficult to comprehend the role of magnetism in our lives as we can’t see them. Take a look around, and realising its importance will not be as difficult. The motors that are used so extensively around the world, whether it’s toy cars or bullet trains or aircraft or spaceships, all use the same magnetic effect.