Under many conditions of use, particularly in institutions such as hospitals, an electrical conductor in the vicinity of the connection to an electrical plug is often jerked laterally with such force that the plug is pulled out of the receptacle with harmful results to the plug and to the receptacle. 
For example, in most hospitals, numerous electrical conductors extend from lamps, call buttons and the like, on a patient's bed to one or more plugs connected to adjcent electrical wall outlets.  Frequently, when the bed must be moved, either to make up the bed or to permit cleaning the floor near and under the bed, the attendant inadvertently fails to remove the plugs from the wall sockets prior to moving the bed.  If, under these circumstances, the extent of the bed's movement exceeds the free length of the conductor, the connecting plug is jerked out of the wall outlet.  Often, the pull on the plug is almost at right angles to the plug alignment, i.e. substantially the entire force component exerted against the plug is parallel to the plane of the wall in which the electrical outlet is mounted.  As a consequence, the outer end of the plug is pulled laterally in the direction of the conductor connection; and at the same time the prongs carried on the inner end of the plug are urged laterally in the opposite direction, the plug being pivoted about a fulcrum located where the rim of the plug is urged inwardly against the underlying receptacle. 
Since most outlets and attendant cover plates are formed of nonconductive "plastic" that is fairly brittle, the wrenching forces exerted by a plug which has been violently jerked sideways often fracture the wall outlet and cover plate to such an extent as to expose the electrically conducting terminals inside the outlet.  Such a condition poses an actionable risk of electrical shock to patients and staff alike. 
It has been found from experience that beds or any equipment moved without careful prior detachment of the plug will destroy both plug and receptacle when the plug is jerked out two or three times at an angle of 45.degree.  or more from the vertical; and even at angles somewhat less than 45.degree.,  not only are the prongs bent but the strength of the prong grip in the receptacle is markedly diminished.