Electric cells exhibit different voltages as a result of the diverse chemical reactions occurring within them.

The voltage, also referred to as electromotive force (EMF), of an electric cell is dictated by the specific chemical reaction that unfolds inside it. This reaction involves the transfer of electrons from one substance to another, a process known as a redox (reduction-oxidation) reaction. Different substances possess varying tendencies to either lose or gain electrons, a characteristic known as electrode potential. The voltage of the cell arises from the difference in electrode potentials between the two substances involved in the reaction.

For example, a standard alkaline cell generates a voltage of approximately $1.5$ volts due to the reaction between zinc and manganese dioxide. In contrast, a lithium-ion cell, which involves a reaction between lithium and cobalt oxide, can produce a voltage of around $3.7$ volts. Thus, the specific substances used and their combinations can significantly influence the voltage produced by a cell.

Furthermore, the design of the cell also impacts its voltage. In a series connection, the voltages of individual cells are summed, resulting in a higher total voltage. Conversely, in a parallel connection, the voltage remains the same as that of a single cell, but the total capacity or available charge is increased.

In summary, the voltage of an electric cell is primarily determined by the chemical reaction occurring within it, which is influenced by the specific substances used and their respective electrode potentials. Additionally, the cell’s design can affect its voltage, especially when multiple cells are interconnected. Understanding these factors is essential for selecting the appropriate cell for various applications, whether it involves powering a small electronic device or an electric vehicle.