Fig. 63
(a) Slow recovery of a wire in a sluggish condition.
(b) Quickened recovery in the same wire after a few vibrations.
Or (2) by heightened response.—The removal of sluggishness by vibration, resulting in increased molecular mobility, is in other instances attended by increase in the height of response, as will be seen from the two sets of records which follow ([fig. 64]). Cold, due to prevailing frosty weather, had made the wires in the cell somewhat lethargic. The records in (a) were the first taken on the day of the experiment. The amplitudes of vibration were 45°, 90°, and 135°. In (b) are given the records of the next series, which are in every case greater than those of (a). This shows that previous vibration, by conferring increased mobility, had heightened the response. In this case, removal of molecular sluggishness is attended by greater intensity of response, without much change in the period of recovery. In connection with this it must be remembered that greater strain consequent on heightened response has a general tendency to a prolongation of the period of recovery.
Fig. 64
(a) Three sets of responses for 45°, 90°, and 135° vibration in a sluggish wire.
(b)The next three sets of responses in the same wire; increased mobility conferred by previous vibration has heightened the response.
It is thus seen that when the wire is in a sluggish condition, successive vibrations confer increased molecular mobility, which finds expression in quickened recovery or heightened response.