Final answer:
The electric field direction is determined by the positive and negative charge placements and typically goes from positive to negative. A uniform electric field between two plates is perpendicular to the plates. The angle of the direction above the horizontal can be found using arctan of the ratio of the vertical to horizontal components.
Step-by-step explanation:
The direction of the electric field at a given point, indicated by a dot in the figure you're referencing, is determined by examining the charges around it. Typically, electric field lines start at positive charges and end at negative charges. In the scenario where the field is uniform, such as between the plates of a capacitor, the lines would be parallel, and the field direction would be perpendicular to the plates, from the positive to the negative plate.
If we need to specify the direction as an angle above the horizontal line, assuming the electric field is horizontal and uniform, the angle would be 0 degrees. If the field is not horizontal, the angle can be found using the provided figure with the vector components Ex, Ey, and Ez. The direction angle E of the electric field vector can be calculated using the tangent of the angle which is the ratio of the y-component to the x-component of the electric field. For instance, if Ex is the horizontal component and Ey is the vertical component, the angle E is given by E = arctan(Ey/Ex).