21 The two different polarities of magnets are identified as north (N) and south (S). The best magnetic materials are iron and its compounds, while most metals such as copper, gold, silver, and aluminium are non-magnetic. The studies leading to the discovery of electromagnetism were done in several steps by different scientists. H. C. rsted discovered that electric current gives rise to magnetism. M. Faraday discovered that magnetism could induce electric currents, and J.C. Maxwell put the whole thing together in a uni ed theory of electromagnetism. ONLINE RESOURCES More applications of electromagnetism loop: anello search coil: bobina di ricerca to wrap: avvolgere 58 elecTriciTy ELECTRICITY AND MAGNETISM Electricity and magnetic fields Electromagnetic field due to the flow of the current Both electricity and magnetism are associated with the movement of electric charges: when N electrons move from one atom to another, they create an electric field around them, causing an electric current. In turn, the moving electric field creates a magnetic field Iin rotating around it. A magnetic field has both a positive and a negative area, which are called positive and negative poles: poles which are the same repel each other, while opposite poles attract each other. Magnets can also attract other objects, made of magnetic materials. The relationship between electric fields and magnetic fields is the basis of electromagnetism. Electromagnetism Electricity and magnetism were studied separately for a long time; however, these two phenomena are strictly related to each other. Let s see how. Let s take a solenoid, a coil of wire wrapped up in a loop. When current flows through it, a magnetic field is generated around it. When a magnet is moved towards or away from it, the changing magnetic field induces a current in the wire and thus an electric current is generated. In other words, there is a close S Solenoid coil Iout relationship between electricity and magnetism. The strength of the magnetic field depends on the amount of current flowing though the wire, and the direction of the current depends on the direction of the movement of the magnet. By adding more windings of wire to a solenoid, it is possible to increase the strength of the magnetic field produced. Applications of electromagnetism The discovery of electromagnetism triggered the invention of the most commonly used devices in everyday life, such as electric motors, generators, and transformers.