The voltaic cell (Fig. 74) consists of a strip of zinc and a strip of copper in a glass jar nearly full of sulphuric acid, supported side by side without touching each other. These two metal strips are connected by a copper wire. Electric current will flow from the copper to the zinc. The copper is called the positive pole and the zinc the negative pole of the cell. The current may be detected by placing the free ends of the copper wire on the tip of the tongue. A slight stinging sensation will be felt, thus proving the presence of an electric current.