With a piece of very fine platinum wire (No. 36 or 40), placed in the
circuit of the battery, the heating effect of the current may be
shown. A half inch of No. 36 platinum wire will serve for the
experiment. If the battery is in good condition it will heat from 1/8
to 1/4 inch of the wire red hot. This is sufficient to light gas or an
alcohol lamp, also to ignite powder or gun cotton.
A short piece of a watch hair spring, or a piece of very fine iron
wire, if placed in the circuit will be made very hot.