Chemistry lesson for the day:

Be careful what you call the cathode and what you call the anode.
Oxidation ALWAYS occurs at the Anode, and reduction always occurs at
the cathode. The oxidation process results in a chemical losing
electrons, and the reduction process results in a chemical gaining
electrons. (Mnemonics: "oxidation" and "anode" both start with
vowels; "reduction" and "cathode" both start with consonants. "LEO sez
GER": Loss of Electrons is Oxidation. Gain of Electrons is
Reduction.) In a cell delivering power, the ANODE is the NEGATIVE
terminal--the electrons given up in the oxidation chemical reaction
come out there. If you re-charge the cell, the roles of anode and
cathode are reversed. You feed electrons into the negative terminal,
and (with luck) cause a reduction reaction where the chemical at that
pole picks up the electrons and is converted back to what it was when
the battery was freshly charged.

Cheers,
Tom


Mark Rand wrote:
On Sat, 09 Sep 2006 16:11:20 -0400, ken scharf
wrote:

bart wrote:
This evening the GF noticed that the remote control wasn't working &
was hot.
I pulled out the extremely hot AA batteries.
It looks like the spring contact in the remote control, on the
negative side had worn away the plastic covering on the side of the
battery & shorted the side metal battery casing to the negative
contact, thereby causing the overheating.
In my many years of battery dissection, I've never seen the side
casing of a battery being positive before!
These were "Golden Power" alkaline batteries, made in China.
They were the original batteries that came with the remote ( for a
Shaw digital cable box).
Anyone ever seen a positive case AA battery before, or is this a new (
dumb) idea?
I've seen many Alkaline batteries with the outside casing connected to
the 'tit' on top as the positive and the bottom flat connector was
insulated from the body of the battery. alkaline batteries have
different chemistry from carbon zinc resulting in an inverted
construction. This may actually be the norm, but in the larger sizes
the plastic outer wrap hides the details. Just looked at a DuraCell
"D" and it is of the inverted construction, but the insulation of the
battery bottom (-) terminal from the case of the battery is hidden
under the plastic wrapping.


Since it's the cathode that gets eaten in whichever reaction is used for the
battery type, it might make sense to have the anode as the case.

I could have done with this 25 years ago when I got sent abroad for work for
three of months and came back to find that the transistor radio batteries had
leaked all over one of my (expensive) loudspeakers :-(

Mark Rand
RTFM

On 14 Sep 2006 10:27:20 -0700, "K7ITM" wrote:

Chemistry lesson for the day:

Be careful what you call the cathode and what you call the anode.
Oxidation ALWAYS occurs at the Anode, and reduction always occurs at
the cathode. The oxidation process results in a chemical losing
electrons, and the reduction process results in a chemical gaining
electrons. (Mnemonics: "oxidation" and "anode" both start with
vowels; "reduction" and "cathode" both start with consonants. "LEO sez
GER": Loss of Electrons is Oxidation. Gain of Electrons is
Reduction.) In a cell delivering power, the ANODE is the NEGATIVE
terminal--the electrons given up in the oxidation chemical reaction
come out there. If you re-charge the cell, the roles of anode and
cathode are reversed. You feed electrons into the negative terminal,
and (with luck) cause a reduction reaction where the chemical at that
pole picks up the electrons and is converted back to what it was when
the battery was freshly charged.

Cheers,
Tom




Guilty as charged (groan).
It's just like my account with the bank where debits remove money instead of
adding money like they should do :-)


Mark Rand
RTFM