An electric charge creates an electric field in the space surrounding it.
When a second charged particle approaches the first, it reacts with it,
indirectly, through the fields created by both particles.
The accepted unit of charge, from the SI (International System), is the
Coulomb (C) which, compared to the charge of an electron (-1.60219E-19 C),
is fairly high.
We can obtain the configuration of an electric field created by a charged
particle by calculating the force at several points on a unit charge (or
test charge) Q.
The electric field is in the same direction as that of the force acting
upon a positive test charge or in the opposite direction as the force acting
on a negative test charge. In this manner the field lines (or lines of
force) are directed from positive charges to negative charges. The
electric field produced by a charge Q is:
where
We can apply the principle of superpositon to the electric field. In this
manner, to calculate the electric field of a system of charges at a given
point, we first calculate the field of each charge in that point and do the
summation:
A way of visualizing an electric field is to spread grass seeds over a
liquid, like oil, and a place two electrodes (a positive and negative)
into the oil. You will see the seeds align with the electric field.
As a note, in the experience
described above as in this computer simulation, we obtain a transversal
view of the field which is in reality three-dimensional.
F
E = --- (newton/coulomb)
q
Q
E = -------------- iR
4*(pi)*E0*R²
Q = value of the static charge creating the field.
R = distance from the charge
E0 = is a constant approximatly 8.854E-12 C²/Nm²
iR= The unit vector uniting the two points under consideration.
Q1 Q2 Qn
E = -------------- iR1 + --------------- iR2 + ... + -------------- iRn
4*(pi)*E0*R1² 4*(pi)*E0*R2² 4*(pi)*E0*Rn²