Students ELECTRODYNAMICS by Lizelle Swanepoel https://padlet.com/lizellexs/p8at90teuo3pu49j en-us 2020-06-12 06:28:12 UTC 2023-09-26 00:06:30 UTC hello@padlet.com https://padlet-assets.s3.amazonaws.com/icons/Bigthunderstorm.png WHAT IS THIS PHENOMENON ILLUSTRATING? lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561314 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561314 OUR STORY STARTS WITH HANS CHRISTIAAN OERSTED lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561316 Danish Professor who discovered the link between electricity and magnetism.]]> 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561316 MAGNETISM lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561317 MAGNETIC FIELD = The region around a magnet where another magnetic material will experience a force.
  • Magnetic field direction is N to S outside the magnet.
  • Magnetic field direction is S to N inside the magnet.
  • Magnetic field lines representing the strength and direction of the magnetic field.
  • Magnetic field lines are continuous lines, forming closed loops.

ONLY THREE METALS ON EARTH ARE NATURALLY MAGNETIC:
  • Fe, Co, Ni. (they are called ferromagnetic)

]]> 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561317 MAGNETIC FIELDS CAN BE PRODUCED BY ELECTRIC CURRENTS lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561318 Magnetic fields are produced by electric currents, which can be currents in wires (or microscopic currents associated with electrons in atomic orbits).

EFFECTS OF AN ELECTRIC CURRENT (I.E. MOVING CHARGE):
  • Heating
  • Magnetism
In electrodynamics we study the magnetic effect resulting from current flowing in a wire.
  • When charge moves in a medium, it generates a magnetic field perpendicularly around that medium.
  • This is electromagnetism (Below is an electromagnet).
]]> 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561318 lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561319 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561319 MAXWELL'S RIGHT HAND GRIP RULE lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561320 The right hand rule is used to find the direction of the magnetic field lines around a current carrying conductor (CCC).]]> 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561320 lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561321 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561321 lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561323 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561323 lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561325 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561325 RIGHT HAND SOLENOID RULE lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561326 Curly fingers = points in direction of current in solenoid.
Thumb = points to NORTH POLE generated by current in the solenoid.]]> 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561326 OR lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561329 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561329 MOTOR EFFECT lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561331 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561331 FLEMING'S LEFT HAND RULE lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561333 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561333 "HANDY" RULES EXPLAINING INTERACTION BETWEEN CURRENTS AND MAGNETIC FIELDS lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561334
  • Right Hand Grip Rule
  • Fleming Left Hand Rule
    • ]]>     2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561334     CURRENT-CARRYING CONDUCTOR PLACED IN 2ND MAGNET FIELD lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561335
  • Both magnetic fields interact. 
  • The magnetic field between the opposite poles and the magnetic field around the current-carrying conductor reinforce each other on one side of conductor 
  • and cancel each other on the other side.
  • A Lorentz force is created = the force acting on the ccc in a MF
    • ]]>     2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561335     lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561336 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561336 HOMEWORK - EX 1 lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561337 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561337 HOMEWORK: ANSWERS lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561338 LET'S MARK!]]> 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561338 THE DC MOTOR lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561339 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561339 lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561340 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561340 lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561341 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561341 HOW A MOTOR WORKS lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561343 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561343 lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561345 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561345 lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561346 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561346 GENERATORS AND ELECTROMAGNETIC INDUCTION lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561347 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561347 MOTOR VS GENERATOR lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561348 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561348 IMPORTANT GENERATOR CONCEPTS lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561349 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561349 FLUX lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561350 Flux = the amount of “something” (electric field, magnetic field) passing through a surface. 

    Total magnetic flux depends on:
    • Strength of the field
    • Size of the surface it passes through
    • Orientation of the surface

    For a loop of area (A) in the presence of a uniform magnetic flux density (B), the magnetic flux (Ф) passing through the loop is:
    • Ф = BA cos θ
      • where θ = angle between magnetic flux density (B) and the normal to the loop of area (A).
      • where B = the magnetic field strength (in Tesla)
      • where A = area of the coil loop
      • Unit for Ф = Wb (Weber)
    ]]>     2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561350     THE COMPONENT OF THE MAGNETIC FIELD VECTOR PARALLEL TO THE NORMAL IS WHAT IS USED IN CALCULATIONS (Bcosθ) lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561351 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561351 MAGNETIC FIELD STRENGTH (symbol B, unit Tesla) lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561352 DEF = magnetic flux density (B) is a representation of the magnitude and direction of the magnetic field.]]> 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561352 ELECTROMAGNETIC INDUCTION lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561353 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561353 FARADAY'S LAW OF INDUCTION lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561354 DEF:
    • Faraday's Law = The emf induced in a coil/conductor is directly proportional to the rate of change of magnetic flux linkage.

    • Flux linkage = The product of the number of turns on the coil and the flux through the coil (NФ)

    The electromotive force (Voltage) generated in a generator is given by Faraday's Law, below.

    Emf is affected by these factors:
    • Number of turns in the coil
    • Rate of change of flux 
    ]]>     2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561354     PARTS OF THE AC GENERATOR lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561355 ALTERNATOR]]> 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561355 DRAW AND INTERPRET GRAPHS OF MAGNETIC FLUX LINKAGE VS. TIME lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561356 For an AC generator, indicating how:
    • the position of the NORMAL TO THE COIL relative to the magnetic field relates to the flux linkage magnitude.
    ]]>     2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561356     LENZ'S LAW lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561358 Def:
    Lenz's Law = The induced current in a coil/conductor flows in a direction so as to set up a magnetic field to oppose the change in the magnetic flux.

    The negative sign in Faraday's law is due to the fact that:
    • The emf induced in the coil acts to oppose any change in the magnetic flux.
    • Work is done to push the permanent magnet against the coil's induced magnetic field.
    • Energy is conserved (Emechanical --> Eelectrical).

    Lenz's Law:
    • gives the direction of an induced EMF which induces a current flow. 
    • the current flows in a direction to oppose the change (an increasing or decreasing magnetic field) causing it.
    ]]>     2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561358     AC GENERATOR lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561359 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561359 FLEMING'S RIGHT HAND RULE lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561360 Use this hand rule to determine the direction of flow of CURRENT induced within the coil.]]> 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561360 lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561361 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561361 GENERATORS - PRINCIPLE OF WORKING lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561362 A generator is a device that converts Ek --> Eelectric. It is a motor in reverse.

    In a motor:
    • A current is passed through a coil in a magnetic field, causing a force and the coil MOVES. A motor works on the principle of the motor effect.

    In a generator: 
    • A coil is rotated through a magnetic field, CAUSING A CURRENT to flow in the coil as the wire cuts across the magnetic field. This causes a changing magnetic field. A generator works on the principle of electromagnetic induction.
    • Induction = the production of current in a conductor as it moves through a changing magnetic field.
    • Faraday's Law of Induction applies in generators, stating that if a wire is moved back and forth in a magnetic field, it cuts across the lines of magnetic flux. This magnetic field pushes on electrons in the metal. This movement of electrons is electrical flow.
    The strength of a generator or motor depends on:
    • "B" - Strength of the magnetic field (flux density of the magnet)
    • "I"  - Current flowing or generated in the coil
    • "ℓ" - Length of the conductor in the magnetic field
    • "θ" - Angle between the conductor and the fixed magnetic field
    • Use this formula for calculations: 
      • F = B x I x ℓ x sin θ    
      • Also: F = Bqv ; q=charge, v=speed of rotor
    ]]>     2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561362     THE AC GENERATOR (ALTERNATOR) lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561363 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561363 lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561364 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561364 lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561365 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561365 lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561366 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561366 AC vs. DC GENERATOR lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561367 AC Generator = An ALTERNATOR
    DC Generator = A DYNAMO]]>     2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561367     lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561369 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561369 lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561370 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561370 FACTORS AFFECTING EMF OF A GENERATOR lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561371 Factors affecting induced emf:
    • Position of the coil
      • If parallel to the external magnetic field (B), then flux lines are not 'cut' and zero induced emf is generated.
      • If perpendicular to an external magnetic field (B), then flux lines are being 'cut' and an induced emf is generated.
    • Strength of the magnetic field
    • Number of turns on the coil
    • Area of the coil
    • Coil wound around an iron core or not.
    • Rotation speed of the coil 
      • i.e. Rate of change in magnetic flux or rate with which coil "cuts" across the permanent magnetic field
    ]]>     2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561371     USES OF AC GENERATORS lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561372
  • Power plants have generators rotated by water or steam.
  • Car alternators charge battery when driving.
  • Diesel/petrol generators as alternative power supply when off-grid.
  • Moving coil microphones use alternators. 
    • Sound waves vibrate a membrane which move a coil in a magnetic field.
    • This induces a varying current which gets amplified and fed to a loudspeaker.
    • ]]>     2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561372     lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561373 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561373 lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561374 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561374 lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561375 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561375 lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561376 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561376 TRANSFORMERS lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561377 Number of turns on the primary and secondary coils affect the input and output voltages.
    This is a step-up transformer.]]>     2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561377     TRANSFORMER EQUATION lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561378 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561378 The Diode & it’s function in AC to DC rectification lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561379 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561379 lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561380 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561380 lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561381 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561381 lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561383 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561383 CERN: WHERE ELECTRODYNAMICS LIVES lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561385 Video]]> 2020-06-12 06:28:12 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623561385 EXERCISE 4 lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623562216 Answer]]> 2020-06-12 06:29:35 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/623562216 lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/631580364 2020-06-18 05:17:27 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/631580364 VIDEO lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/662313973 2020-07-25 10:03:35 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/662313973 ELECTROSTATIC VS GRAVITATIONAL FIELDS IN ACTION - BUILD YOUR OWN PARTICLE ACCELERATOR! lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/662318072 2020-07-25 10:30:36 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/662318072 ELECTRICAL POWER lizellexs https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/662320937 2020-07-25 10:49:39 UTC https://padlet.com/lizellexs/p8at90teuo3pu49j/wish/662320937