875 
EN V with respect to Ee 
the electromotive force V is proportional to the magnetic induction. 
Generally it will be impossible to measure V with an oscillographic 
electrostatic instrument. But we can use a galvanometric oscillograph 
at the terminals of C. We shall then get the connections shown in 
fig. 5 and the differential equations become: 
I dB 
Saati, and &—-+4 ri Ri, ss. (4) 
We eliminate t, and get 
If we may disregard the expression 
dB 4 dV f 1 1 \ (5) 
DE | BROS rt 
r Y 
in which A en After integration this becomes: 
gr er ns (6 
zn — + — Lane da 
eld A ) 
We find a linear expression connecting B and V if the integral 
in (6) need not be considered. This is allowed if both RC and rC 
are very large and if also the frequency per second is high enough. 
With a periodic change of B, which 
might be represented by a Fourier 
series, the value for the integral during 
one period = 0. We have only to 
soe examine its value during one period. 
j With a frequency of 50 per second 
Fig. 6. and time constants CR and Cr of 
0.2 second each we get for a potential curve as represented by the 
; 
EE TEE en 
AT ee meen tn REC 
57% 
