You're probably already familiar with
the concept that positive and negative
charges attract while like charges repel.
This attraction or repulsion has been
observed to act over a distance with no
contact between individual elements.
Fields describe non-contact forces, so we
can use a field to describe the
interactions between charged particles.
In short, charged particles create
electric fields. Let's look at the
electric field surrounding a positive
charge. Electric fields point in the
direction that positive particles
experience a force. A positive particle
would be repelled from this positive
charge, so we know the direction that the
electric field will point away from the
positive charge. Imagine that, there is a
positive particle right on top of the
charge. They would hate being next to
each other, so they would repel quite
strongly. Now imagine that there is a
positive particle at the other end of
the universe, the repulsion these two
particles will experience is very small.
Since the repulsion is due to the
electric field, and the repulsion gets
smaller the further away you are, then
the strength of the electric field also
gets smaller the further way you are. So
this is the electric field surrounding a
positive charge represented with vectors.
We can also use field lines to represent
the electric field, the vectors closer to
the charge are bigger in magnitude,
meaning that the electric field closer
to the charge is stronger. So field lines
should be more dense closer to the
charge and less dense further out. So
this is the electric field surrounding a
positive charge represented with field
lines. A negatively charged particle will
have an electric field with the exact
same shape as a positive particle.
However, the field lines will point in
the opposite direction. This is because
electric field lines point in the
direction that a positive particle will
travel. So for a negative particle, the
field lines will point towards the
particle.
