(Section 5-3)
Coulombs law involves the
quantifying
(putting numbers to) of the attraction of unlike charges and the
repulsion of
like charges. There are two aspects
that should be obvious to us. First,
the greater the charges, the greater the repulsion or attraction.
If I am a proton, with a 1+ charge, a particle with a 2+ charge
should be
twice as repulsive to me as a particle with a 1+ charge.
The second aspect is that the attraction/repulsion decreases
with
distance. If I am a proton, with a 1+ charge, I will be more repulsed
by a
particle with a 1+ charge right next to me than a particle with a 1+
charge 100
yards away.
The results of experimentation show that this effect can be quantified with the following equation:
where Q1 and Q2 are the charges, K is a constant (9 x 109 N m2/C2 ) and r is the distance between the charges in meters.
Shouldn't the protons in a nucleus
repel each other and fly apart?
The helium nucleus contains two protons. They repel each other. Why doesn’t the helium nucleus break apart? The answer is very unsatisfying. There is another force called the "binding force" or "nuclear force" that holds the nucleus together. One can imagine that this is a very strong force and it is the energy from this force that we tap in to in nuclear reactions.
On the other hand, the electron is held together with the protons in the nucleus by the electrostatic force. The force of gravity between the masses of the nucleus and the electron is negligible compared to the electrostatic force in the atom.