The electric field vector is not directly applicable to waves on a string because it is a concept used to describe electromagnetic waves, not mechanical waves like those on a string.
In the context of electromagnetic waves, such as light waves, the electric field vector represents the direction and magnitude of the electric field at each point in space as the wave propagates. It is perpendicular to the direction of wave propagation and also perpendicular to the magnetic field vector, with both fields oscillating in mutually perpendicular planes.
For mechanical waves on a string, such as transverse waves, the appropriate concept is the displacement or amplitude of the wave, which represents the maximum displacement of the string from its equilibrium position. The displacement of the string is perpendicular to the direction of wave propagation, meaning it oscillates perpendicular to the string's length.
It's important to note that the electric field vector is not directly relevant to mechanical waves on a string, as they are governed by different physical principles.