Читать книгу Introduction To Modern Planar Transmission Lines - Anand K. Verma - Страница 19

So far, we have paid attention to the electrostatics. At this stage, Leiden jar was the only source of static electricity. A source for the continuous electric current was not available. Volta in 1799 invented the voltaic pile, i.e. a chemical battery, and the first time a continuous source of electric current came into existence. On April 21, 1820, it led to the discovery of the magnetic effect of current flowing in a wire. The electric current became the source of the magnetic field, encircling the current‐carrying wire. The magnetic effect of current was discovered by Orsted (Oersted). In the same year, Ampere showed that the co‐directional parallel currents flowing in two wires attract each other, and the counter‐currents repel each other. It was a very significant discovery, i.e. creation of the attractive and repulsive magnetic forces without any physical magnet. It firmly established the relation between electricity and magnetism. Ampere further developed an equation, presently called Ampere's Circuital Law, to connect the current flowing in a wire to the magnetic field around it and developed the right‐hand rule. He called the new field of electricity Electrodynamics and Maxwell recognized him as the Father of Electrodynamics. Ampere further modeled the natural magnetic materials as the materials composed of perpetual tiny circulating electric currents. He demonstrated the validity of his concept using the current‐carrying conductor in the helical form called a solenoid. The solenoid worked like an artificial bar magnet. In the year 1820 itself, Biot–Savart obtained the equation using the line integral to compute the magnetic field at a position in the space due to the current flowing in a wire [J.2, B.6, B.7].