The magnetic field is a property of the space that surrounds an electric current and a magnet. In early physics powdered iron was used to visualize its geometric character, and the distributed field intensities were studied with a compass needle. However, such observations were hardly subject to systematic investigations, until a coiled wire became available for studying a uniform magnetic field at a measurable intensity. Indicated by a ripple pattern of iron particles, the field-lines revealed the distribution in space, which were recognized as significant for describing the nature of a magnetic field. Faraday (1832) made a number of sketches of field-lines emphasizing the significance of a distributed pattern, and he discussed the field with the concept of flux of field-lines. In fact, in the previous chapters we used his idea for electric fields for which electric charges on conductors were responsible. For a magnetic field, in contrast, we cannot argue further using electric analogies because magnetic charges are absent in nature. Nevertheless, with the concept of flux Faraday described the induction effect in magnetic fields, which lead him to establish the fundamental laws of electromagnetism. Owing to Faraday’s discovery, the flux of magnetic field-lines, as determined by induced voltages, allows a quantitative description of the magnetic field with no responsible magnetic charges.
KeywordsMagnetic Induction Magnetic Force Alternate Current Induction Current Search Coil
Unable to display preview. Download preview PDF.