Tip:
Highlight text to annotate it
X
To solve big problems, sometimes it's needed a different point of view.
For example, at the beginning, the electric interaction was understood like an action
at a distance. Grosso modo, we have to charges and... bam! They feel attracted or repeled
inmediatly, without any kind of contact. Such a force doesn't differ to scifi's telekinesis.
However, a new idea was born; it was a concept which will change the way we perceive physics'
interactions. The idea is quite simple: we can imagine that
common things perturb their surroundings by giving them some properties, some influence
that can "be felt" by other bodies. For instance, in electricity: place a positive
charge at a point in space and take a "prove charge", 1C charged, and place it in another
point. This last charge will feel a force because of the electric interaction. So what
we do is take that force and attach it to the point where the "prove charge" felt it.
If we do the same with all points in space, we'll obtain a kind of map that can show us
what will happen if we put a charge at any point. This "map" is the Electric Field.
One way to draw the field without so many vectors is using FIELD LINES. We just draw
lines according to the field direction, and voilà! Now we have the paths to be followed
by any positive charged placed there. It's important to mention that field lines
start at positive charges and ends at negative ones. The same happens with the Magnetic Field,
where field lines start at north's pole and go to the south's one. Magnetic field is born
as electric field does, but instead of charged, we observe how small magnets orientate. By
the way, do you remember those strange trajectories that cause magnet interaction? Using fields
it's easier to understand it. We have a charge with a certain velocity,
feeling a certain magnetic field. If we rotate the velocity vector around by the shortest
way, we can determinate where the force will point: this force is called Lorentz Force.
Clockwise: inside. Anticlockwise: outside. This force is like a rope tying the charge
and making it to rotate around a point. Here there are the curved paths!
Field is such an extraordinary useful idea, that physicians firmly believe in its physical
reality. In fact, this is one of the most important supporters of modern physics. We
have talked here only about classical fields, but in modern physics there are ultra-precise
theories, like Standard Model, based on quantum fields. Don't worry about that, we'll see
it later. Just know that quantum fields' excitations are common elemental particles.
But going back to classical electromagnetism: the idea of "field" allowed last century's
physicians to join the physics hide behind the electric and magnetic interactions in
only four equations... In fact, they can be reduced to two, and almost in one...
But... if you want to understand them, subscribe and watch it in new videos, and thanks for
watching!