Physics

A force is that which tends to cause a change in the size or shape of a body or in its state of motion.

A summary of the results of these observations is given in the following laws of refraction: I. When light enters a transparent body, perpendicularly, it passes on without changing its direction. II. When light enters a denser transparent body obliquely, it is bent toward the perpendicular; when light enters a less dense body obliquely, it is bent away from the perpendicular.

In studying the production and distribution of static electricity it was seen that if two bodies at different potentials are connected by a copper wire a movement of electricity to the body having the lower potential occurred along the conducting wire. This movement of electricity is called an electric current