Electricity and Magnetism free essay sample

As he was setting up his materials, he noticed acompass needle  deflected from  magnetic north  when the electric current from the battery he was using was switched on and off. This deflection convinced him that magnetic fields radiate from all sides of a wire carrying an electric current, just as light and heat do, and that it confirmed a direct relationship between electricity and magnetism. At the time of discovery, Orsted did not suggest any satisfactory explanation of the phenomenon, nor did he try to represent the phenomenon in a mathematical framework. However, three months later he began more intensive investigations. Soon thereafter he published his findings, proving that an electric current produces a magnetic field as it flows through a wire. The  CGS  unit of  magnetic induction  (oersted) is named in honor of his contributions to the field of electromagnetism. His findings resulted in intensive research throughout the scientific community in  electrodynamics. We will write a custom essay sample on Electricity and Magnetism or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page They influenced French physicist  Andre-Marie Amperes developments of a single mathematical form to represent the magnetic forces between urrent-carrying conductors. Orsteds discovery also represented a major step toward a unified concept of energy. This unification, which was observed by  Michael Faraday, extended by  James Clerk Maxwell, and partially reformulated by  Oliver Heaviside  and  Heinrich Hertz, is one of the key accomplishments of 19th century  mathematical physics. It had far-reaching consequences, one of which was the understanding of the nature oflight. Light and other  electromagnetic waves  take the form of  quantized, self-propagating  oscillatory  electromagnetic field disturbances called  photons. Differentfrequencies  of oscillation give rise to the different forms of  electromagnetic radiation, from  radio waves  at the lowest frequencies, to visible light at intermediate frequencies, to  gamma rays  at the highest frequencies. Orsted was not the only person to examine the relation between electricity and magnetism. In 1802  Gian Domenico Romagnosi, an Italian legal scholar, deflected a magnetic needle by electrostatic charges. Actually, no  galvanic  current existed in the setup and hence no electromagnetism was present. An account of the discovery was published in 1802 in an Italian newspaper, but it was largely overlooked by the contemporary scientific community. Electricity and Magnetism Electricity and magnetism is an interesting aspect of electricity. We are familiar with in our everyday lives with the phenomenon of static cling when two objects, such as a piece of Saran wrap and a wool sweater, are rubbed together, they cling. One feature of this that we dont encounter too often is static repulsion if each piece of Saran wrap is rubbed on the wool sweater, then the pieces of Saran wrap will repel when brought near each other. These phenomena are interpreted in terms of the objects acquiring anelectric charge, which has the following features: * There are two types of charge, which by convention are labelled  positive  and  negative. * Like charges repel, and unlike charges attract. * All objects may have a charge equal to an integral number of a basic unit of charge. * Charge is never created or destroyed. Electric Fields A convenient concept for describing these electricity and magnetism forces is that of an  electric field. Imagine that we have a fixed distribution of charges, such as on the plate below, and bring in the vicinity of this distribution a  test chargeQ. Figure 1  Test charge in the presence of a fixed charge distribution This charge will experience a force due to the presence of the other charges. One defines the electric field of the charge distribution as: The electric field is a property of this fixed charge distribution; the force on a different charge  Q  at the same point would be given by the product of the charge  Q  and the  same  electric field. Note that the electric field at  Q  is always in the same direction as the electric force. Because the force on a charge depends on the magnitude of the charges involved and on the distances separating the charges, the electric field varies from point to point, both in magnitude and direction. By convention, the direction of the electric field at a point is the direction of the force on a  positivetest charge placed at that point. An example of the electric field due to a positive point charge is given below. Figure 2:  Electric field lines of a positive charge Power and Magnetic Fields An electricity and magnetism phenomenon apparently unrelated to power are electrical magnetic fields. We are familiar with these forces through the interaction of compasses with the earths magnetic field, or through fridge magnets or magnets on childrens toys. Magnetic forces are explained in terms very similar to those used for electric forces: * There are two types of  magnetic poles, conventionally called North and South * Like poles repel, and opposite poles attract However, this attraction differs from electric power in one important aspect: * Unlike electric charges, magnetic poles always occur in North-South pairs; there are nomagnetic monopoles. Later on we will see at the atomic level why this is so. As in the case of electric charges, it is convenient to introduce the concept of a  magnetic field  in describing the action of magnetic forces. Magnetic field lines for a bar magnet are pictured below. Figure 3:  Magnetic field lines of a bar magnet One can interpret these lines as indicating the direction that a compass needle will point if placed at that position. The strength of magnetic fields is measured in units of  Teslas  (T). One tesla is actually a relatively strong field the earths magnetic field is of the order of 0. 001 T. Magnetic Forces On Moving Charges One basic feature is that, in the vicinity of a magnetic field, a  moving  charge will experience a force. Interestingly, the force on the charged particle is always perpendicular to the direction it is moving. Thus magnetic forces cause charged particles to change their direction of motion, but they do not change the  speed  of the particle. This property is used in high-energy particle accelerators to focus beams of particles which eventually collide with targets to produce new particles. Another way to understand these electricity and magnetism forces is to realize that if the force is perpendicular to the motion, then no work is done. Hence these forces do no work on charged particles and cannot increase their kinetic energy. If a charged particle moves through a constant magnetic field, its speed stays the same, but its direction is constantly changing. A device in which this property is used is the  mass spectrometer, which is used to identify elements. A basic mass spectrometer is pictured below. Figure 4:  Mass spectrometer In this device a beam of charged particles (ions) enter a region of a magnetic field, where they experience a force and are bent in a circular path. The amount of bending depends on the mass (and charge) of the particle, and by measuring this amount one can infer they type of particle that is present by comparing to the bending of known elements. Magnet Power From Electric Power A connection was discovered (accidentally) by Orsted over 100 years ago, who noticed that a compass needle is deflected when brought into the vicinity of a current carrying wire.