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Electricity & Magnetism

Electricity & Magnetism. W. Sautter 2007. A Moving Charge in a Magnetic Field. Centripetal force On charge caused By magnetic field. Palm = force Exerted on The charge. +. N. Fingers = magnetic flux lines North to South. Thumb = direction of + charge Motion (current).

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Electricity & Magnetism

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  1. Electricity & Magnetism W. Sautter 2007

  2. A Moving Charge in a Magnetic Field Centripetal force On charge caused By magnetic field Palm = force Exerted on The charge + N Fingers = magnetic flux lines North to South Thumb = direction of + charge Motion (current) Charge moves in a circular path

  3. Electric Motor armature Magnets

  4. Magnetic Lines of Flux N (magnet) S By convention (everybody agrees) lines of magnetic Flux leave the North pole and enter the South pole Lines of flux are continuous and do not intersect each other.

  5. Power Generators at Hoover Dam

  6. Direction of induced field N LENZ’S LAW When a magnet induces a current flow in a conductor, the induced current flows in a direction so as to create a magnetic field in the conductor that opposes the original magnet field Conductor Wire loop Current in loop N S Motion of magnet Using the Right Hand Rule

  7. Right Hand Rule for Current Flow Direction of conventional current flow (fingers) North end of Induced Magnetic Field (thumb)

  8. Induced EMF in a Conductor Conductor is Moved upward In magnetic field Palm = motion of conductor in magneticfield Induced EMF N Fingers = magnetic flux lines North to South Thumb = direction of induced current in the conductor

  9. Force = Bqv sin  E.M.F. = Blv sin u B = I 0  ______________ 2 r

  10. Units Used in Magnetism Calculations • F = Force (newtons) • B = Magnetic field strength (teslas) • Tesla = N / amps x meters • L= conductor length (meters) • V = velocity of conductor thru field (meters/sec) • Q = charge quantity (coulombs) • = angle between conductor and field measured from the perpendicular (degrees) r = distance from the magnetic field source (meters) • u0 = permittivity constant of material • (Free space = 8.85418782 × 10-12 m-3 kg-1 s4 A2 • or 8.85418782 × 10-12 T x m /A • n = loops of conductor

  11. n voltage in coil Voltage in coil current in the coil Transformers Secondary Voltage out n= number of turns of wire in the coil Primary Voltage in

  12. Energy Transfer in a Transformer Secondary coil current Magnetic field Primary coil The magnetic field caused by the changing current in the primary coil radiates across the secondary coil and induces a current in it. current A continually changing current in the primary is required for a transformer to work (D.C. will not work)

  13. THE END

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