dication that the cell is fully charged.

Relations Between Chemical Actions and Electricity.

We know now that chemical actions in the battery produce electricity
and that, on the other hand, an electric current, sent through the
battery from an outside source, such as a generator, produces chemical
changes in the battery. How are chemical changes and electricity
related? The various chemical elements which we have in a battery are
supposed to carry small charges of electricity, which, however,
ordinarily neutralize one another. When a cell is discharging,
however, the electrolyte, water, and active materials are separated
into parts carrying negative and positive charges, and these "charges"
cause what we call an electric current to flow in the apparatus
attached to the battery.

Similarly, when a battery is charged, the charging current produces
electrical "charges" which cause the substances in the battery to
unite, due to the attraction of position and negative charges for one
another. This is a brief, rough statement of the relations between
chemical reactions and electricity in a battery. A more thorough study
of the subject would be out of place in this book. It is sufficient
for the repairman to remember that the substances in a battery carry
charges of electricity which become available as an electric current
when a battery discharges, and that a charging current causes electric
charges to form, thereby "charging" the battery.

========================================================================

CHAPTER 5.
WHAT TAKES PLACE DURING DISCHARGE.
----------------------------------

Considered chemically, the discharge of a storage battery consists of
the changing of the spongy lead and lead peroxide into lead sulphate,
and the abstraction of the acid from the electrolyte. Considered
electrically, the changes are more complex, and require further
investigation. The voltage, internal resistance, rate of discharge,
capacity, and other features must be considered, and the effects of
changes in one upon the others must be studied. This proceeding is
simplified considerably if we consider each point separately. The
abstraction of the acid from the electrolyte gives us a method of
determining the condition of charge or discharge in the battery, and
must also be studied.

[Fig. 21 Graph: voltage changes at end and after charge]

Voltage Changes During Discharge. At the end of a charge, and before
openi