How Does a Dry Cell Produce Electricity?

Every battery has positive and negative terminals allowing electrons to flow, producing electricity.

A dry cell battery converts chemical energy into electricity. The chemical reaction produces electrons, which then collect at the negative terminal of the battery. When there is a connection between the positive and negative terminal, the electrons flow to the positive terminal. This electron flow is what we experience as an electric current.

Definition

An electrolyte is a solution capable of conducting electricity. In a dry cell battery, the electrolyte is in the form of a paste just moist enough to allow current to flow. Dry cell batteries can operate in any position because the electrolyte solution does not spill. Most dry cell batteries use an ammonium chloride paste.

Composition

Almost all dry cell batteries contain the same parts: a metal electrode or graphite rod surrounded by a moist electrolyte paste enclosed in a metal cylinder.

Electron Flow

All matter consists of atoms, and all atoms are positively charged protons, neutral neutrons and negatively charged electrons. Think of the electricity produced by a dry cell battery as the flow of electrons temporarily separated from atoms. Batteries take advantage of this flow of electrons by providing a chemical reaction that separates the electrons from atoms, and by providing a negative terminal where these negatively charged elements collect.

Chemical Reaction

The chemical reaction that powers the battery is a "redox" reaction. Redox means a gain or loss of electrons. Inside the battery, electrons combine with cations at the cathode (the central metal or graphite rod), while electrons detach from anions at the anode (the surrounding metal casing).

Positive and Negative Terminals

Electrons have a negative charge. Oppositely charged particles attract. That is why, whenever they have the chance, electrons will flow from a place of negative charge to a place of positive charge. This flow is electricity.

In a dry cell battery, the metal cylinder enclosing the electrolyte paste is the negative terminal. It is typically a zinc anode. The positive terminal is typically a carbon cathode. When there is a connection made between the zinc anode and the carbon cathode, electrons flow from the negative to the positive terminal, producing electric current.

Electrons must flow from the negative terminal to the positive for the chemical reaction to take place. When there is no connection between the terminals, no electrons flow, and no chemical reaction happens. That is why a dry cell battery can sit on your shelf for years without going dead. Once you connect the terminals, the electricity starts flowing.

Common Types

The two most common types of dry cell battery are the zinc-carbon battery and the alkaline battery. Typically, an alkaline battery has a much longer life because the zinc anode corrodes less rapidly in a basic (alkaline) solution than it does in an acidic (ammonium chloride) solution.

References

• Euro Chlor: Battery Basics
• University of Hawaii: Dry-Cell Battery