Magnetic fields
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Magnetic Fields. Forces, Magnetic Field Lines Electron Flow Left Hand Rule Right Hand Rule. Interactions of a Magnetic Field. Direction : the lines of magnetism start from the North Pole and return to the South Pole

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Magnetic fields l.jpg

Magnetic Fields

Forces, Magnetic Field Lines

Electron Flow

Left Hand Rule

Right Hand Rule

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Interactions of a Magnetic Field

  • Direction : the lines of magnetism start from the North Pole and return to the South Pole

  • Magnetic Flux Lines: these imaginary field lines show the direction of force within the field. The standard SI unit is a WEBER

  • Flux Density: the amount of force compared to the amount of current (I) in Amperes

  • Permeability : materials have the ability to concentrate the FLUX lines. The permeability of a VACUUM and AIR is one.

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German physicist Wilhelm Eduard Weber

  • A popular theory of magnetism considers the molecular alignment of the material. This is known as Weber's theory

  • A more modern theory of magnetism is based on the electron spin principle.

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Uses of the “Tesla Coil”

  • He went to the United States in 1884 and worked for American inventor Thomas Edison for a year before setting up his own workshop. For much of his time in the United States, Nikola Tesla worked with American industrialist George Westinghouse, who bought and successfully developed Tesla's patents, leading to the introduction of alternating current for power transmission

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Calculations of Magnetism

  • B = Force/Ampere-Meter or

  • B = Webers / Meter2 or

  • B = tesla*

  • The unit is named after Croatian-born American electrical engineer Nikola Tesla

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V is the Voltage


N are the number turns in the coil

p (primary)

s (secondary)

Vp = Np

Vs Ns

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Transformer problem

  • The primary on transformer has 1200 turns. How many turns should the secondary have if the voltage changes from 220 volts to 110 volts?

    Vp = Np

    Vs Ns

    220 = 1200


    Ns = 600 Turns

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Left hand Rule

The Left Hand Rule shows what happens when charged particles (such as electrons in a current) enter a magnetic field.

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Example question Electron Movement in Magnetic Fields on Paper

  • An electron enters a uniform magnetic Field

Velocity = 6.0 x 10 7 meters per second

The Flux density is 4.0 x 10 –2 tesla directed INTO the page

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Find Direction and PaperMagnetic Force

  • Using the Left HAND RULE :thumb points electron’s Force Downward, Pointing Finger point moving Electron into the page, and the Magnetic Field lines into the page (X).

  • F = qvB

    = (1.6x 10 –19 C) (6.0 x 10 7 m/s) (4.0 x 10 –2 telsa)

    = 3.0 x 10 –13 N

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Single Wire Magnetic Field Paper

The Right Hand Rule, illustrated below, simply shows how a current-carrying wire generates a magnetic field.

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Magnetic Coil with Solenoid Paper


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Summary Paper

  • Magnetic Force is a force that exists between charges in motion.

  • Electrons generate magnetic fields by their spin.

  • Permeability of magnetic materials change the flux density of the field

  • Left hand determines the direction of the field, force, and electron movement or when any charged particles enter a magnetic field.

  • Right hand rules how a current-carrying wire generates a magnetic field