Electricity and Magnetism

Description

Electricity is related to charges, and both electrons and protons carry a charge. The amount of the charge is the same for each particle, but opposite in sign. Electrons carry a negative charge while protons carry positive charge. All electromagnetic fields are force fields, carrying energy and capable of producing an action at a distance. These fields have characteristics of both waves and particles. An electric current flowing in a wire or coil produces its own magnetic field. A compass needle will swing at right angles to the wire. What is the difference between an electric field and a magnetic field? Actually both are usually all around us, since they are present wherever there is electricity. Both an electric and a magnetic field exist around power lines, appliances, light fixtures, and electric wiring; but electromagnetic fields are generated only when current is flowing through a wire. The voltage on a wire produces electric fields. Ferromagnetism and ferrimagnetism occur when the magnetic moments in a magnetic material line up spontaneously at a temperature below the so-called Curie temperature, to produce net magnetization. The magnetic moments are aligned at random at temperatures above the Curie point, but become ordered, typically in a vertical or, in special cases, in a spiral (helical) array, below this temperature. This book is written mainly for the physics student, although it will also be useful for the students of electrical and electronic engineering. The approach is concise but clear. The theory, however, is set out in a completely selfcontained and coherent way and developed to the point where the reader can appreciate the beauty and coherence of the Maxwell equations.