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Kenneth Buckle, a visiting scientist at the Center
for Integrated Manufacturing Studies at the Rochester
Institute of Technology, provides this answer:
When connected to a load like a lightbulb, a typical battery
undergoes chemical reactions that release electrons, which
travel through the bulb and are then reabsorbed by the battery.
(Devices that store mechanical energy also exist, but the most
common bat ter ies ,  such as those used in fl  ashlights and   remotes,
hold energy in chemical form.) Inside is at least one galvanic
cell, which produces between zero and several volts,   depending
on its chemistry. In a car battery, six cells, each contributing
two volts, are connected in series to make a 12-volt battery.
All electrochemical cells consist of two electrodes separated
by some distance. The space between the electrodes is fi  lled
with an electrolyte, a liquid or
solid containing charged par-
ticles, or ions. One electrode—
the anode—emits negatively
charged electrons. The other—
the cathode—receives them.
Chemical differences between
the two electrodes create an en-
ergy difference, or potential,
that moves electrons from the
anode to the cathode via the
electrolyte. For example, the lead-acid cell uses a lead oxide
cathode, a lead anode and a sulfuric acid (liquid) electrolyte.
In this case, sulfuric acid creates an environment that
stretches the chemical bonds of the lead and lead oxide, so
oxidation and reduction reactions occur simultaneously. In the
reduction reaction the acid strips the oxygen from the lead-
oxide cathode and replaces it with sulfate. The oxide ion then
combines with hydrogen (from the acid) and forms water. In
oxidation the sulfuric acid coaxes two electrons away from the
lead and then latches on to form lead sulfate. If the battery is
attached to a load, the electrons that the sulfate replaces   travel
out of the cell and into the load, creating an electric current.
A galvanic cell can continue to discharge electrons until
either or both electrodes run out of reagents, the compounds
that drive the oxidation/reduction reactions. In a nonrecharge-
able battery the chemical reaction that created the energy is
not easily reversible, and when the reagents run out the cell is
unusable. In a rechargeable battery, such as the lead-acid cell,
the reaction is reversible, meaning that an external source of
direct electric current can force the electrons to fl  ow from the
cathode to the anode until the cell is recharged.
Does damp weather make
arthritis pain worse?
—C. Levy, Falls Church, Va.
Donald A. Redelmeier, a professor of medicine at
the University of Toronto, explains:
Despite the commonly held notion that dampness contrib-
utes to joint aches, decades of medical research show no ob-
jective relation between arthritis severity and weather.
Dampness, decreases in barometric pressure and high hu-
midity are characteristics that some people believe contribute
to fl  ares in arthritis pain, but similar environmental changes
experienced during other situations do not seem to affect suf-
ferers one way or the other. For instance, arthritis patients do
not experience dramatic increases in symptoms when bathing
or swimming. Patients easily tolerate greater swings in pres-
sure during a plane ride than would occur during a storm.
Still, no past study investigating the link between weather
and arthritic pain is fl  awless; research has neither totally ruled
out nor established a connection. Evidence of a causal link
requires dispassionate observation wherein neither clinicians
nor patients know what exposure is active. Clinicians and pa-
tients would have to ignore weather—a diffi  cult task.
Studies suggest people see patterns even where none exist.
By chance, some rainy days will be followed by pain, en-
trenching the belief in a connection. Ultimately, such beliefs
reveal more about the workings of the mind than those of
the body