71 force field. "Originally a term coined by Michael Faraday to provide an intuitive paradigm, but theoretical construct, for the behavior of electromagnetic fields, the term force field refers to the lines of force one object (the "source object) exerts on another objector ab bcollection of other objects. An object might be amass particle or an electric or mag- netic charge, for example. The lines do not have to be straight, in the Euclidean geometry case, but maybe curved. Faraday called these theoretical connections between objects lines of force because the objects are most directly connected to the source object along this line. Examples of force fields A local Newtonian gravitational field near Earth ground typically consists of a uniform array of vectors pointing in one direction---downwards, towards the ground its force field is represented by the Cartesian vector , where points in a direction away from the ground, and m refers to the mass, and g refers to the acceleration due to gravity. A global Gravitational field consists of a spherical array of vectors pointing towards the center of gravity. Its classical force field, in spherical coordinates, is represented by the vector, , which is just Newton's Law of Gravity, with the radial unit vector pointing towards the origin of the sphere (center of the Earth. A conservative Electric field has an electric charge (or a smeared plum pudding of electric charges) as its source object. In the case of the point charges, the force field is represented by , where is the position vector that represents the straightest line between the source charge and the other charge. A static Magnetic field has a magnetic charge (a magnetic monopole or a charge distribution. The electromagnetic force is given by the Lorentz force formula, which in SI units is, ." -- Reference Wikipedia.org back to 71)