Mindmap

Magnetism

Mark White Física Cuarto Spanisch

Inhalt der Mindmap

Magnetism

History and Impact
- 600 BC (Lodestones)
  - Greeks discovered that they attract themselves and metallic objects
- XIII BC (Compass)
  - Chinese made the compass
- Oersted (Danish)
  - Electric current conductor wire diverted a compass needle (1820)
    - André Ampère made some similar experiments
- Michael Faraday and Joseph Henry
  - Electromagnetic induction
    - A magnet moving near to a conducting coil produces a spiral current
Magnetic Interaction
- Greeks discovered magnetite that atrracted pieces of not magnetized iron
  - Magnetism
    - Force of attraction that is experimented
  - Magnet
    - Object that exerts the magnetic force
      - Electron motion in a organized way
    - Poles
      - Regions with more concentration of force
      - Law of Magnetic Force
        Repel
        Equal magnetic poles
        Attract
        Different magnetic poles
      - If a magnet is cuted in half
        Magnet always have north and south pole
        No matter its size
        Weaker in small pieces
        Poles cannot be isolated
    - Magnetic Field
      - Vector Field
        Magnitude
        Direction
        From north to south pole
        Inward from its south pole
        Points outward from its north
      - A charge generates an electric field around it and also a magnetic field if the electric field it is moving
        If a charge is moving inside an external magnetic field, the field produced by the moving charge will interact and exert a force
        Magnetic force on a moving charge
        Magnetic field B and moving charge q interact
        q has a velocity v
        Vector
        Direction
        Given by the right hand rule
        Right Hand
        Positive Charges
        Left Hand
        Negative Charges
        Pointing with four fingers in the direction of the magnetic field with the hand extended, curling them in the direction of the particles motion (direction velocity)
        Thumb indicate the direction of the force
        Magnitude
        Magnetic Force
        Whe acts over a postive charge q moving at velocity v, is perpendicular to v and magnetic fiel B
        For given values of velocity and intensity of a magnetic field, the force is greater when they are perpendicular.
        The resulting force in conductors produces a moment of torsion with radius (r)
        Useful for the calculation of electric motors
        By the interaction between two bodies are produced by the interaction between moving electrons in the atoms that make up the bodies
        Electromagnetic Theory
        Force in a current carrying conductor
        If the charge charge is distributed along a conductor
        Wire or conductor with a length L
        That moves with a velocity v
        Rearranging terms
        q/t can be replaced with current (I)
        Force over the conductor is:
        Vector
        Direction
        RHR
        Magnitude
      - Space in which magnetic effects are present
        Magnetic Field Lines
        Visualize magnetic fields
        Just as electric field lines describes electric fields
Magnetic Field Sources and Oersted´s Experiment
- Permanent
  - Magnetite
- Non-Permanent
  - Electromagnet
- Danish scientist found that the Electric Current produces a Magnetic Field
  - Produce torque over the compass
  - First connection between Electricty and Magnetism
Biot-Savart Experiments (Biot and Savart - Physicists)
- Calculate the Magnetic Field (B) produced by any any type of current flowing on a wire
  - By performing the experiments of Magnetic Fields near to different kinds of circuits
  - Superposition Principle for Magnetic Fields
    - “The total magnetic field produced by several moving charges is the vector sum of the fields produced by individual charges”
      - Integral is the addition of the contributions to the total magnetic field done by very small segments of the wire were the current is flowing
    - Geometry
      - Long Current-Carrying conductor
      - Circular Coil (Center), magnetic induction is perpendicular to the plane of the coil
        N Number of Windings (Center)
      - Circular Coil with N Number of Windings (Any Distance in the Center Axis)
      - Inside a Solenoid
        Coiled wire with many helical turns
        Or Toroid Doughnut-Shaped
  - Hall Effect Sensor
    - Experiment used to measure Magnetic Fields
      - Prove Biot-Savart Formula
Electricity and Magnetism
- Electric Charge at Rest = Electric Field
- Electric Charge is Moving = Electric and Magnetic Field
Examples
- Our planet as a giant magnet
- Aurera Borealis
- Electronic Devices
  - Loudspeaker
  - Printer
  - Electric motor
  - Television
  - Hard Disk
  - Magnetically levitated trains
- MIR
  - Magnetic Resonance Imaging
    - Strong magnetic fields and radio frequency (RF) waves
      - Form images of body
      - Diseases detected
        Tumors
        Brain Infection
        Multiple Sclerosis
Ampere’s Law
- High Simmetry
  - Relation between Magnetic Field and Electric Current
    - RHR (Positive Direction)
  - Easier than Biot-Savart Law
- Current Stable
  - No Magnetic Materials or Electric Fields around