Apparatus. Same as in [Exp. 142], the acid, however, being but 1 in. deep in the tumbler; that is, we have the effect of a cell with small plates, each being about 1 in. by ½ in.
360. Directions. (A) Repeat (B) and (C) of [Exp. 142], recording the reading of G V in each case.
(B) Compare the results with those of [Exp. 142], remembering that the internal resistance is larger than before. Is the current as strong with small plates as with large plates when the external resistance is small? When the external resistance is small (the 5-turn coil, for example), should the cell have a high or low internal resistance to produce the greatest effect upon the needle?
EXPERIMENT 144. To find whether the changes in current strength, due to changes in internal resistance, are as great when the external resistance is large, as they are when the external resistance is small.
Apparatus. Same as for [Exp. 142], 143, also the rheostat containing the two meters of G-s wire ([Exp. 121]).
361. Directions. (A) Arrange as in [Fig. 109], the external resistance being 2 meters of No. 30 G-s wire in series with G V. The 2-F C in the Fig. is replaced, however, by the simple cell as in [Exp. 143].
(B) Find the effect upon the strength of the current of moving the plates about when but 1 in. of acid is in the tumbler.
(C) Nearly fill the tumbler with acid and repeat (B), taking readings with plates near each other and as far apart as possible. Lift them nearly out of the acid and take the reading.