i'm trying to understand electric fields and electric potential better. electric potential is voltage and electric fields are vectors. I think the electric field would be zero in the middle between two positive charges (vectors cancel).
You're correct that the electric field at any point in space can be described as a vector, and this is because electric field simply represents an experienced
force per unit charge, and force is obviously a vector quantity. As a result, vector addition holds in determining the electric field. Considering a test charge existing at the exact midpoint between two identical positive charges in space, with no other charges present, the test charge will indeed experience no net force, and so there is effectively no electric field present at this point (i.e. the electric field has a magnitude of 0 N/C). As a consequence of the vector nature of the electric field, the electric field at any point can be broken into component vectors. For the example above, the electric field vector components clearly end up canceling each other out.
When would the voltage between two particles be zero?
Similarly, the electric potential or voltage is the
electric potential energy per unit charge experienced at that point in space. Similar to how a massive body will have no gravitational potential energy if it is not present in a gravitational field, a charged body will have no electric potential energy if it is not present in an electric field. To put that a different way, if the electric field at a point is zero, the voltage at that point is zero. Thus, hopefully it is clear that for the midpoint between the positive charges described above, the voltage at that point in space is zero.
I also read somewhere [the electric field is] 0 along equipotent lines, can someone explain why?
However, if the electric field at a point is non-zero, then voltage must be considered in the context of a reference point (similar to how gravitational potential energy is considered in the context of the earth for objects in the earth's gravitational field.) For voltage we set that reference point
at an infinite distance. When we consider the set of points in an electric field for which the voltage is the same, we can plot
equipotential lines. If we set a reference point at a nearer spot when calculating voltage, say in the area of concern rather than at an infinite distance away, we can calculate the voltage difference (∆V) between the two points. Since the set of points along an equipotential line is defined as that set for which "absolute" voltage is the same, there must be zero voltage difference between that set of points. This indicates that no work would be required to move a charged body along the equipotential line.
The implication is that the electric field
along the equipotential line is zero, since moving a charge along the line requires no work
it must not be moving against any electric field in either direction along the line. But wait, the electric field isn't zero at the points on the line, because those points are present in the electric field of the point charge, right? Yes, but that net field is a vector sum of its components. The electric field component vectors
along the equipotential line for any point on the line are zero, but perpendicular to the line the electric field component vectors are non-zero.
Stated more plainly, the electric field component vector(s)
tangent to a point on an equipotential line are zero.
Would [the voltage] be zero exactly between a positive and negatively charged particle? Voltage is a scalar though, so i'm not sure why that'd be the case.
Nope! There would be a non-zero net electric field between the two oppositely-charged particles, so the voltage at that point would be non-zero.
