What is a galvanic cell?

A galvanic cell is defined as an electrochemical cell that generates electrical energy through spontaneous chemical reactions. In this type of cell, two different metals are typically involved, connected by an electrolyte. The oxidation (loss of electrons) occurs at the anode, while reduction (gain of electrons) takes place at the cathode. This flow of electrons between the two electrodes creates an electric current, which can be harnessed to do work, such as powering electronic devices.

The spontaneous nature of the chemical reactions is critical to the function of a galvanic cell; it means that the reaction can occur without any external energy input, making it a sustainable source of electrical energy. This principle is widely applied in batteries that power a variety of devices, making galvanic cells fundamental to the field of electrochemistry.

This understanding distinguishes galvanic cells from other devices listed in the options, which do not fundamentally derive electrical energy from spontaneous reactions. For example, consuming external energy or being used for measurement purposes does not characterize a galvanic cell.