MAGNETISM - Florida State University

MAGNETISM - Florida State University

MAGNETISM Historical background: lodestone (magnetite) known for 1000s of years; Thales of Miletus studied lodestones (590 BC); magnetic compass invented by Chinese around 200 AD; Pierre de Maricourt a.k.a. Petrus Peregrinus (1269) studied magnets, Earth's magnetism; concept of poles, tried to isolate single pole; William Gilbert (1544-1603) (court physician of Elizabeth I and James I) first serious studies of magnets two poles of magnets Earth is a magnet iron can be magnetized magnetism destroyed by heating Hans Christian Oersted (1777-1851) electric current generates magnetic field (1820) Essentials of magnetism: every magnet has two poles - dipole''-- there are no magnetic monopoles like poles repel each other, unlike poles attract magnetic field: magnetic forces due to magnetic field (Faraday), caused by magnet in its surrounding magnetic field lines describe direction, density of lines represents magnitude of field;

field due to one pole obeys Coulomb-like law, total field of magnetic dipole = superposition of the two fields moving charges (currents) generate magnetic fields MAGNETISM OF MATERIALS: origin of magnetism: atoms can have magnetic dipole field, partly due to effects of orbital motion of electrons, but mainly due to electron spin (intrinsic angular momentum of electrons); in most materials, atoms have no net dipole field, or directions of elementary dipoles random effects cancel; in some materials (ferromagnetic materials), many atomic dipoles aligned magnetic domains; if domains not aligned, material is not magnetic; if domains aligned, material is magnetic, strong magnetic field can align domains magnetization if domains stay aligned after magnetizing field turned off permanent magnet magnetically soft materials do not retain

magnetization; used for electromagnets EARTH'S MAGNETIC FIELD Earth is a magnet north-seeking pole of compass needle called (by arbitrary definition) a northpole the Earth's northern magnetic pole is actually a magnetic south pole Earth's geomagnetic poles are not at geographic poles, positions change in time; presently, magnetic N is about 13o (i.e. about 1500km) from geographic N declination = angle between geographic (true) N and magnetic N; 15o E in Los Angeles, Las Vegas, Salt Lake City; 0o in Houston, Tulsa, Omaha 3o W in Tallahassee; 15o W in Boston, Montreal inclination = magnetic dip = angle between horizontal plane and magnetic field vector; magnitude of Earths magnetic field: at Tallahassee: 49.4T at Washington, DC 53.4T at Fairbanks, Alaska: 57.0T

Recently Viewed Presentations

  • Representation structures in West Community Health and Care

    Representation structures in West Community Health and Care

    Representation structures in West Community Health and Care Partnership Public Partnership Forum West CHCP PPF West CHCP Has a PPF and a Local Service User Network LSUN The LSUN structure relates to Community Care Service Users and Carers and links...
  • Examining Teachers Efficacy in Mathematics Teaching: A Pilot

    Examining Teachers Efficacy in Mathematics Teaching: A Pilot

    Examining Teachers' Efficacy in Mathematics Teaching: A Pilot Study. Natalie A. Tran1, David Drew2, Mark Ellis1, Ruth Yopp-Edwards1, . Mike Matsuda3, and Martin Bonsangue1. 1California State University, Fullerton. 2Claremont Graduate University. 3Anaheim Union High School District. NSF Robert Noyce Teacher...
  • Snímek 1 - JNV

    Snímek 1 - JNV

    ŘÍDÍCÍ SYSTÉMY CNS NEUROENDOKRINOLOGIE NEUROIMUNOLOGIE HYPOTHALAMICKÉ HORMONY Systémy (osy) H-A-P Doposud bylo identifikováno 5 neuroendokrinních systémů primární hypothalamický hormon (RH nebo IH) odpovídající sekundární hormony adenohypofýzy Sekundární hormony z adenohypofýzy - uvolňovány do oběhu LH luteinizační hormon FSH folikuly stimulující...
  • Electric Vehicle Integration into the Grid

    Electric Vehicle Integration into the Grid

    Electric Vehicle Integration into the Grid. Joseph Flanagan. 11/17/14. NPRE 498-ES. Outline. Vehicle Electrification ... and RG Pratt. 2007. "Impacts Assessment of Plug-in Hybrid Vehicles on Electric Utilities and Regional US Power Grids: Part 1: Technical Analysis." ... Improved battery...
  • Concentrative and Equilibrative Drug Transport

    Concentrative and Equilibrative Drug Transport

    Principles of Clinical Pharmacology January 9, 2003 Module 2: Drug Metabolism and Transport Unit 6: Concentrative and Equilibrative Drug Transport
  • Before we start  Please complete the Pre-Assessment Military

    Before we start Please complete the Pre-Assessment Military

    PG 15 - Sometimes when drafting a crosswalk, multiple credentials are shown. There can be 20-30 related credentials to specific occupations. You will need to do research for the specific occupation and look at job listings to determine specific requirements.
  • Introduction To Robot Sensors Introduction to Sensors What

    Introduction To Robot Sensors Introduction to Sensors What

    Introduction To Robot Sensors. When - after students have learned about Boolean expressions and relational operators. Goal - students to develop a mental model of how robots make decisions . The lesson includes: an introduction to sensors
  • Cloning Vectors

    Cloning Vectors

    Vectors . Vector is an agent that can carry a DNA fragment into a host cell in which it is capable of replication. If it is used only for reproducing the DNA fragment, it is called a cloning vector.If it...