﻿Electric Waves obtained by Valves. 



169 



For brevity, the adjustable circuit will be referred to as 

 the rods. It is not possible to graduate the rods in wave- 

 lengths as against extension of the arms, as this wave-length 



Fig-. 4. 



depends on the emission and on the plate volts. Thus with 

 a fixed length of the arms and 44 volts between grid and 

 plate : 



(1) With plate potential fixed. 



Emission 2*2 m.a. \ = 311 cm. 



6-8 306 



9-8 300 



(2) With emission constant at 5*2 m.a. 

 Plate potential 1*2 volts. \ = 308 cm. 



2-4 314 



- Hence for a given setting X decreases as the emission rises, 

 and increases as the plate voltage is increased. This is due 

 to the fact that the plate and grid are not a potential node of 

 the oscillating system, but are a variable distance from it 

 depending on the alternating voltage necessary to sustain 

 the oscillation, and this in turn depends on the emission and 

 plate voltage. It is not, however, necessary to go further 

 into this, as the wave-lengths were always found directly by 

 a secondary circuit as in Paragraph 6, the rods being used 

 as a convenient way of varying continuously the wave-length 

 of tire system connected to the valve. With all the other 

 factors fixed, the rods were pulled out a centimetre at a time 

 and the oscillating current and wave-length recorded for 

 each position. In one experiment the emission was 1*5 m.a.. 

 the orrid potential 44 volts, the plate potential 1'8 volts, and 

 oscillations were maintained from X = 320 cm. to X = 451cm. 

 with a maximum oscillation about A, = 323 cm. It was 

 always found that the maximum oscillation was close to the 

 short-wave end of the rane^e. 



