214 ELEMENTS OF ELECTRICITY AND MAGNETISM. 



the electrical field outside of the vessel does not depend in any 

 way upon the position of the body B inside the vessel, and, if 

 the body B is brought into contact with the wall of the vessel, 

 the lines of force which emanate from B disappear, no charge is 

 left on B and no charge is left on the inner surface of the 

 vessel. 



120. Giving up of entire charge by one body to another. 

 When the body B, Figs. 144, 145, 146, and 147, is lowered 

 into the vessel and allowed to touch the walls of the vessel it loses 

 all of its charge and remains without charge when removed from 

 the vessel, and the charge on the outside of the vessel is equal to 

 and of the same sign as the original charge on B. The body B 

 may thus be said to give up its entire charge to the vessel. 



121. Convective discharge and disruptive discharge. Consider 

 the positive and negative charges at the ends of a bundle of lines 

 of force. In order that these charges may disappear, it is neces- 

 sary that the lines of force be annihilated. This may be accom- 

 plished by the moving of the charged surfaces towards each other 

 until they are coincident, or the dielectric which sustains the elec- 

 trical stress may break down. In the former case, we have what 

 is known as connective discharge, and, in the latter case, we have 

 what is known as disruptive discharge. 



Convective discharge is to some extent analogous to the re- 

 lieving of a stretched rubber band by allowing its ends to move 

 towards each other. Disruptive discharge is somewhat analo- 

 gous to the relief of a stretched rubber band by rupture. 



Examples. (a) Two metal plates A A and BB in Fig. 106, 

 being disconnected from the battery, might be discharged 

 (the electric field be made to disappear) by moving the plates 

 together. 



(&) The transfer of charge by a moving ball, as described in 

 Art. 94, is convective discharge. The ball gathers in the ends 

 of a bundle of lines of force when it touches one plate and it 

 shortens these lines until they disappear as it moves across to the 



