Page:Collected Physical Papers.djvu/263

cyclic variation was small, (2) when the range was comparatively large (c. f. Tables IV and V).

Table IV.—Showing the Variation of Current and Resistance with Cyclic Electromotive Variation of Small Range

E. M. F. in volt.	Galvanometer readings. 1dn=1/106 amp.				Resistance in ohms
	Direct.		Return.		Direct.		Return.
0·05 0·10 0·15 0·20 0·25 0·30	$\downarrow$	10·0 25·5 47·0 70·0 103·0 171·0	12·0 27·0 49·5 75·5 114·5 197·5	$\uparrow$	$\downarrow$	5,000 3,920 3,191 2,856 2,427 1,754	4,166 3,703 3,030 2,648 2,183 1,520	$\uparrow$
	$\to$				$\to$

It has been shown that the resistance of the receiver at the higher E. M. F. is less than that at the lower. As the E. M. F. is reduced by the reversed motion of the slider, there is a tendency towards the recovery of the higher resistance which it had at the lower E. M. F. The recovery, however, is not perfect, owing to hysteresis. The recovery is more incomplete if the critical E. M. F. had been exceeded.

There is thus a residual after-effect. In the case given, the initial resistance was 5,000 ohms, and the resistance after cyclic variation through a range of 0·25 volt was 4,166 ohms, or 8/10ths of its original value.

The lag and creeping effects are also noticeable in the forward and return readings.