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Mass m is the mechanical attribute of an object.
*** Mass is not the mechanical attribute of an object.
There are other mechanical attributes such as size,
shape, and density.
It determines how the object accelerates (F=m*a) and
*** It partially determines how an object accelerates .....
how it is attracted by another mass (F=G*m*M/d^2).
*** and how moves in an electric or gravitational field.
The first electric phenomenon discovered was mutual
attraction and mutual repulsion of light objects under
the influence of something which was not mass or
magnet.
*** How do you know that this was the "first"
That property, named charge, was initially modeled as a fluid.
An object containing that fluid was said to be electrified.
*** What was the date and circumstance of the initial modelling
of the property called charge?
Likewise, a plastic rod rubbed with wool repels
another plastic rod rubbed with wool. But an
electrified glass and an electrified plastic attract,
rather than repel, each other.
*** The attraction (or repulsion) of a charged piece of
glass and a charged plastic rod is very tricky. It depends
on the type of plastic, its temperature, and the amount of
rubbing that is done.
This observation, and many other observations, led
to a realization that there are two kinds of electric
fluids, positive and negative.
*** I wonder if static charges should be called "electric
fluids" at this point.
The term charge used to be interpreted as the "amount of
electric fluids" or "amount of electricity" which an
object can acquire or lose.
A modern interpretation is based on the realization
that submicroscopic particles, protons and electrons,
are permanently charged with positive and negative
electricity. A macroscopic object is charged when the
number of electrons and the number of protons are not
identical. An excess of protons results in a net positive
charge while an excess of electrons results in a net
negative charge.
*** Doesn't the above statement conflict with the idea
that the quantity of protons remains fixed within an atom
of glass or rubber. Isn't a negative charge associated
with a surplus of electons surrounding the nucleus and
a positive charge associated with a deficiency of such
electrons?
The net charge, like the total mass,
becomes an attribute of an object. It is an attribute
responsible for forces between electrified objects.
*** But isn't it true that the the total mass of an
object is much less likely to change than its net charge.
Two similar charges (both positive or both negative)
always repel but two dissimilar charges (positive and
negative) always attract. This was the first qualitative
observation about electric forces.
*** Is it the "charges" that repel or attract or is it the
"charged objects" that do the repelling and attracting?
It turns out that the magnitude of an electric force
between two charges (q1 and q2) is proportional to
the product q1*q2 and inversely proportional to the
square of the distance (d^2) between their centers. This
observation, made by Coulomb, is known of Coulomb’s
law. It can be written as:
F = k*q1*q2 / d^2
where k is the proportionality constant. The value of
that constant can be chosen arbitrarily in order to
define a unit of electric charge. For the purpose of this
introduction the unit of electric charge, one coulomb, C,
we will defined by declaring that k=1,000,000,000.
*** Iszn't it important to state the units (newton-meters
squared over coulombs squared) in the definition of k here?
This is equivalent to saying that the electric charge is one
coulomb if it attracts or repels an identical charge with
a force of one billion newtons when the distance between
the centers of two charges is one meter. One coulomb is
a very large charge; charges produced on robbed rods
and plates are usually expressed in microcoulombs or in
nanocoulombs. Ignoring sign differences we can say
that the charge of one electron and the charge of one
proton are identical (1.6*10^-19 C).
The so-called "official" SI definition of the unit of charge
is conceptually different from the one presented above.
But in practical terms it is not at all different. In SI the
ampere, A, is the first unit;
*** It would be better to say that the ampere is a defined
in the SI system as a "fundamental" unit rather than a
"first" unit. The terms fundamental and first are not really
synonomous.
I hope that my "***" comments are helpful for your purpose.