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  1. Electromagnetism University of British Columbia Physics 420 By: Jason Cheung

  2. What is a Field? • A region of space characterized by a physical property having a determinable value at every point in the region • Examples: gravitational field, Electric field ,and magnetic field

  3. Gravitational Field • Defined as A = acceleration G = gravitational constant r = distance to the center of the big object m = mass of big object

  4. Electric field is defined as the electric force per unit Charge It is the surrounding charges that create an electric field Electric Field E = Electric Field F = Electric Force q = Charge E is measure in Force/Coulomb

  5. Cathode Ray Tube Demo (CRT)

  6. Magnetic Field • Magnetic field is a field that exerts a force on a moving charge • A magnetic field can be caused either by another moving charge or by a changing of electric field or magnetic dipoles of materials

  7. Magnetic Field is measure in Tesla A simple formula to calculate Magnetic Field B = magnetic field F = Magnetic Force Q = charge V = velocity of the moving charge

  8. Battery Demo

  9. Charge moving in a magnetic field obeys the Right Hand Rule • There are two types of RHR • Right Hand Rule #1 • Right Hand Rule #2

  10. Right Hand Rule 1 • The thumb represents the velocity of which the charge is going • The remaining fingers tell you the direction of the magnetic field • example:

  11. Right Hand Rule 2 • I = direction of the charge • B = direction of the Magnetic Field • F = Force act on the charge • Palm Push Positive (*Remember!!)

  12. Right Hand Rule Question

  13. What is magnetism? Magnetism is one of the phenomena by which materials exert an attractive or repulsive force on other materials. What causes magnetism in material? It is the unpaired electrons in the electron orbit cause magnetism Magnetism example of pair and unpaired: N is unpaired, O is paired (one of them)

  14. Remember SPDF?? (Chem 11) • Electrons fall into electron shell according to Hund’s rule. • Examples

  15. Nitrogen -Electrons -Protons and Neutrons 1s2 2p3 2s2 Right Electron Configuration of Nitrogen Wrong Wrong

  16. 1.Ferromagnetic 2.Paramagnetic 3.Diamagnetic 4.Ferrimagnetic (Not going to cover) There are four types of magnetism

  17. Magnetism is Measure in Magnetic Susceptibility (χm) The more susceptibility of a material has, the more magnetic property it processes

  18. Ferromagnetic • Any material that possess magnetization WITHOUT an external magnetic field is ferromagnetic • large and positive susceptibility • Examples of ferromagnetic materials • Iron (Fe) • Susceptibility = 200 • Cobalt (Co) • Susceptibility = 70

  19. Iron electron configuration Fe: 1s2,2s2,2p6,3s2,3p6,4s2,3d6 Ar: 1s2,2s2,2p6,3s2,3p6 = [Ar] “Core” Fe: [Ar],4s2,3d6 [Ar] -The electrons seems to align spontaneously -Pure quantum mechanics effect

  20. Why are some Ferromagnetic doesn’t attract one another? • Has to do with the magnetic domain of the material

  21. Ferromagnetic material demo

  22. Paramagnetic • Any material that possess magnetization (i.e. attraction with other magnetized material) WITH an external magnetic field is paramagnetic • small and positive susceptibility • Examples of paramagnetic materials Aluminum Al Susceptibility = 2.2*10-5 Platinum Pt

  23. Aluminum electron configuration [Ne].3s2.3p1 What is the differences between the two?! Compare to Iron (Fe) [Ar] Fe: [Ar],4s2,3d6 the dipoles do not interact with one another and are randomly oriented in the absence of an external field due to thermal agitation, resulting in zero net magnetic moment

  24. Paramagnetic and Ferromagnetic Demo (magnets and levitation)

  25. Diamagnetic • very weak and negative susceptibility to magnetic fields. • Negative susceptibility = repel against magnetic fields (diamagnetism) • Positive susceptibility = attract to magnetic fields (para + ferromagnetism)

  26. Diamagnetism • Examples of diamagnetic materials Gold Human (mostly) Copper

  27. Diamagnetic Levitation Demo

  28. Applications of Magnetism MRI (magnetic resonance images) Superconductors

  29. Applications of Magnetism • Maglev Trains