When we talk about electric components, one ‘battery’ on its own is called a cell. Two or more cells stacked together are called a battery.
Cells and batteries are sources of electrical potential energy. They can transfer their chemical energy into electrical energy.
The flow of electric current is from the positive (+) to the negative (–) end of a battery.
Learn about the electrolytes in Earth and Space 22.3
z A simple cell (or single cell) is made up of two different metals, called electrodes, placed in a chemical. This chemical can be in the form of a liquid or a paste called an electrolyte.
Fig. 18.6.4
A simple cell can be made from a copper and zinc plate (electrodes) placed in dilute sulfuric acid solution and connected to a bulb
Copper electrode
Zinc electrode
sulfuric acid (electrolyte)
z The more cells connected to each other in a battery, the greater the potential difference of the battery.
Fig. 18.6.5 The circuit symbol for a battery made up of many simple cells
Fig. 18.6.6 A car battery has many electrodes placed in a liquid chemical
Dilute
Positive plates
Negative plates
Dilute sulfuric acid
A chemical reaction happens inside every cell or battery. This leads to a build-up of positive charges at one electrode and negative charges at another electrode.
If these electrodes are connected by wires to a bulb, they now have a point of low energy to ‘drop’ to. In other words, we have created a potential difference and the charge can flow.
