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Anode and Cathode confusion?

Discussion in 'Electronic Equipment' started by WAYNEL, Jan 2, 2007.

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  1. WAYNEL

    WAYNEL Guest

    Can any one give a good explanation that is not so confusion concerning
    the anode and cathode, relating to rechargable batteries and cells.


    At the cathode of a cell you get a reduction and at the anode you get
    oxidation.
    Electrons flow into cathode of the cell and thus produce a high
    alkiline around the electrode, OH-.
    Although on a Porbaix diagram the most negative side has a H+?

    In electronics the cathode is negative and the anode in positive and
    electrons travel from negtive to positive therefore the positive
    (anode), when charging, will connect to the to the cathode of the
    battery and cathode to anode of a battery???

    Cheers

    WayneL
     
  2. Electron flow is normally (forget zeners) from cathode to anode and
    conventional current flow is opposite.

    Diodes used as rectifiers used to have the cathode marked with a + symbol to
    denote the positive end of the load circuit.

    To turn on a diode (forget zeners) make the anode positive with respect to
    the cathode.
     
  3. WAYNEL

    WAYNEL Guest

    Several hours of searching revieled a good explanation which furthers
    what the Green book
    http://www.iupac.org/publications/books/gbook/green_book_2ed.pdf
    says.
    A chemistry nomenclature
    http://www.ktf-split.hr/glossary/en_s.php?def=cathode

    States.

    cathode

    Cathode is a negative electrode of an electrolytic cell to which
    positively charged ions (cations) migrate when a current is passed as
    in electroplating baths.

    In a primary or secondary cell (battery or accumulator) the cathode is
    the electrode that spontaneously becomes negative during discharge, and
    form which therefore electrons emerge.

    In vacuum electronic devices electrons are emitted by the cathode and
    flow to the anode.



    WayneL
     
  4. Merriam-Webster online has this definition for cathode:
    1 : the electrode of an electrochemical cell at which reduction occurs:
    a : the negative terminal of an electrolytic cell b : the positive
    terminal of a galvanic cell
    2 : the electron-emitting electrode of an electron tube; broadly : the
    negative electrode of a diode

    The definition for anode is the mirror image of this.
    Galvanic cells are batteries, and electrolytic cells are loads.
    Electrical diodes are loads and the terminals are named like those of
    electrolytic cells.
     
  5. Bob Masta

    Bob Masta Guest

    In chemistry class (back when there were only 4 elements)
    the mnemonic that worked for me was that an "anion" was
    "A Negative ION."

    Hope this helps!



    Bob Masta
    dqatechATdaqartaDOTcom

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    www.daqarta.com
    Scope, Spectrum, Spectrogram, Signal Generator
    Science with your sound card!
     
  6. Charles Jean

    Charles Jean Guest

    ___

    In electrolysis situations, I usually remember polarities by:

    RED CAT
    REDuction is the process occurring at the CAThode.
    Therefore, oxidation must be the process occurring at the anode.

    LEO GER
    Substances Losing Electrons are Oxidized. Substances Gaining
    Electrons are Reduced.

    By knowing the two mnemonics, RED CAT and LEO GER you've got it all.

    If you took two carbon rods and stuck them into a copper chloride
    solution, you could predict which one would produce the chlorine gas
    and which one would have copper plated on it:

    Cu+2 + 2e- ---> 2Cu
    copper has GAINed electrons. GER. REDuction has occurred. This
    must be the CAThode. Copper will be plated here when electrons are
    supplied from a battery's electron supply side or (-) pole.

    2Cl- ---> Cl2 + 2e-
    chlorine has Lost Electrons. LEO. Oxidation has occurred. This
    must be the Anode. Chlorine gas will be generated here when connected
    to the battery's electron deficient side or (+) pole.
     
  7. Bob Masta

    Bob Masta Guest

    The mnemonic we learned for that is "LEO the lion roars, GER"

    Best regards,




    Bob Masta
    dqatechATdaqartaDOTcom

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    www.daqarta.com
    Scope, Spectrum, Spectrogram, Signal Generator
    Science with your sound card!
     
  8. Guest

    The following is taken from the "Electrochemistry Dictionary"
    http://electrochem.cwru.edu/ed/dict.htm

    rechargeable battery
    A battery in which the chemical reaction system providing the
    electrical current is easily "chemically" reversible. After
    discharging, it can be recharged by applying an electrical current to
    its terminals. Some batteries can be recharged hundreds to thousands
    times. See, e.g. the lead-acid battery. Also called "secondary"
    battery, and "accumulator." Contrast with non-rechargeable battery.

    It operates as a galvanic cell during discharge and as an electrolytic
    cell during charge. As a consequence, the anode is the negative
    electrode during discharge, while it is the positive electrode during
    charge; at the same time, the cathode is the positive electrode during
    discharge, while it is the negative electrode during charge. This can
    create a confusing situation, and it is preferable to refer to the
    electrodes of a rechargeable battery as "positive" and "negative,"
    because this designation is independent of the operational mode.
    Unfortunately, this nomenclature is not always followed. Often the
    "negative" electrode is designated as anode and the "positive"
    electrode is designated as cathode. This naming convention is a
    carry-over from the convention of the non-rechargeable battery.


    Good luck: ZN
     
  9. jasen

    jasen Guest

    I find OIL RIG more connvenient:
    Oxidation Is Loss, Reduction Is Gain.

    Bye.
    Jasen
     
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