an imaginary line or curve in a field of force, as an electric field, such that the direction of the line at any point is that of the force in the field at that point.
an imaginary line representing a field of force, such as an electric or magnetic field, such that the tangent at any point is the direction of the field vector at that point
A line used to indicate the direction of a field, especially an electric or magnetic field, at various points in space. The tangent of a line of force at each point indicates the orientation of the field at that point. Arrows are usually used to indicate the direction of the force. See Note at magnetism.
