EXPERIMENT 145. To find the best way to join two similar cells when the external resistance is small.
Apparatus. Two simple cells using dilute sulphuric acid, with copper and zinc elements, as in [Exp. 112]; galvanoscope, G V; connecting wires, etc. Have the zincs well amalgamated. Remove them from the acid as soon as readings are taken.
366. Directions. (A) Partly fill the tumblers with the acid. Join the cells in series ([Fig. 110]), then connect wire 1 ([Fig. 110]) with the left-hand binding-post of G V, and wire 2 with the middle one, thus putting the 5-turn coil into the circuit. Take the reading of G V.
(B) Join the cells in multiple arc ([Fig. 111]), connecting them as in (A) with G V. Write down the reading, and compare it with that found in (A).
(C) Take the reading with but 1 cell joined to G V.
EXPERIMENT 146. To find the best way to join two similar cells when the external resistance is large.
Apparatus. Same as for [Exp. 145], also the rheostat containing 2 metres of No. 28 or 30 G-s wire. Arrange the G-s wire in series with the 15-turn coil of G V, as shown in [Fig. 109], two simple cells being used, however, instead of 2-F C as shown.
367. Directions. (A) Take the reading of G V when the two cells are in series ([Exp. 145]), the external resistance being the 15-turn coil and G-s wire.
(B) Join the cells in parallel and take the reading, using the same external resistance as in (A).