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1. Oersted's Obeservations In the, year 1819, a Danish school teacher named Oersted discovered that a magnetic field is produced surrounding a conductor carrying a current. If magnetic needle is suspended parallel to a conducting wire, the needle experiences a force deflecting it when a current is passed through the wire, showing that magnetic field is produced in the region surrounding the wire. Direction of the field is such that the needle tends to align prependicular to the length of the wire carrying the current. These observations of Oersted were presented to the French academy by Arago on 11 Sept., 1820. 2. Biot-Savrat's Law Within a short period of two months of this discovery, Biot and Savart made a quantitative study of this effect, and on the basis of this study deducted the law relating the strength of the current and the length of the conductor with the strength of the magnetic field generated. Satish K. Gupta, op. cit. p. 391– “Magnetic Effect of Current In 1820, the Danish scientist Oersted discovered the magnetic effect of electric current. Oersted's experiment led to the discovery that when electric current passes through a conductor, magnetic field is produced around it. If a strong current is passed through a conductor, then magnetic field produced around the conductor is also very strong and the earth's magnetic field may be neglected in its comparison. In such a case, magnetic lines of force near the conductor are found to be aircular. When electric current is passed through a circular conductor, the magnetic field lines near the centre of the conductor are almost straight. Laplace's Law or Biot-Savart Law Laplace's law is used to know the magnitude of the magnetic field at a point near a conductor carrying current. This law was first experimentally confirmed by Biot and Savrat and for this reason, it is sometimes referred to as Biot-Savart's law. J.S. Zaveri and Muni Mahendra Kumar, Microcosmology ... , pp. 14, 15“Discovery of Electromagnetic Phenomena
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