THE PHENOMENA OF ELECTROSTATICS. 207 



carriers are fixed. Stationary neutralizing rods are placed one 

 on each side of the machine, each inclined at an angle of approxi- 

 mately 45 to the horizontal, and the charge on one disk as it 

 travels towards the collectors serves as the inducing charge for 

 the other disk. 



The inducing action of the Wimshurst machine may be ex- 

 plained as follows : Figure 133 represents two glass plates AB 



?B 



Fig. 133. 



and CD. One of these plates is charged as indicated by the 

 plus signs, and the lines of force from this charge converge upon 

 the metal point P which is at one end of a neutralizing rod. 



p \ 



L-\ \ 



The electric field in the neighborhood of P is sufficiently intense 

 to break down the air between P and the glass plate CD, thus 

 leaving negative charge on the glass plate CD as shown in 



Fig. 134- 



The small portion of the surface of CD which faces the point 

 P is thus negatively charged and the amount of charge on this 

 small portion is numerically equal to the amount of positive 

 charge on the larger part of AB from which emanate the lines 

 of force that have been broken down between P and CD. If 

 the plate CD is moved to the left in Fig. 1 34, fresh lines of 

 force crowd into the space between the point P and the plate 

 CD, they continue to break down as in the first instance, and the 

 entire surface of CD, as it moves out from under the point 



