﻿Motion of Electrons in Argon and in Hydrogen. 1045 



When moving along its free paths between collisions the 

 mean velocity of an electron in the direction of the electric 

 force is W ; and since all directions of motion are equally 

 probable after a collision, the mean velocity in the direction 

 of the force is zero after a collision and 2W before a collision. 

 The loss of energy in a collision is therefore 2mW 2 . When 

 variations in the mean free paths and the velocities are taken 

 into consideration, it is found that the fraction \of its mean 

 energy of agitation mu 2 /2 which an electron loses in a collision 

 is given approximately by the formula 



■46 



W ! 



(5) 



The following table gives the mean velocity of agitation u, 

 and the velocity in the direction of the electric force in 

 argon for different values of the ratio Z/p and the values of 

 / and X obtained from the above formulae. Since I and X 

 depend directly on the energy of agitation which is pro- 

 portional to k, the. values of Z/p are chosen to correspond to 

 definite values of k. The values of I are for the gas at 

 one millimetre pressure. 



Table III. 



k. 



Z/p. 



wxio- 5 . 



«xio- 7 . 



11-5 



ixio 2 . 



X x 10 5 . 



1 



no 



•125 



CM 



o ± 



20 



179 



120 



■195 



325 



126 



14-7 



1-64 



140 



•275 



3-4 



136 



11-8 



1-54 



160 



•355 



36 



145 



10-3 



1-52 



180 



•440 



3-85 



15-4 



944 



1-54 



200 



•525 



4-15 



16-3 



9-02 



1-60 



240 



•71 



4-85 



17-8 



8-52 



1-82 



280 



•95 



6-0 



193 



8-52 



2-38 



3-20 



1-25 



7-7 



20-6 



8-88 



345 



310 



5 



40 



20-2 



11-3 



9-7 



324 



10 



65 



20-7 



942 



243 



324 



15 



82 



20-7 



7-92 



38 6 



10. The large values of k obtained in argon are due to 

 the fact that the loss of energy of an electron in a collision 

 with a molecule is extremely small, as shown by the figures 

 in the last column. This loss is* very much less than in 

 hydrogen or nitrogen. When moving with a velocity of 

 agitation 12*0 x 10 7 cm. per sec, the fraction of its energy 

 lost by an electron in a collision with a molecule is 16 x 10 "'"' 

 in argon, 5xl0" 2 in nitrogen, and 4xl0 -2 in hydrogen. 



