In order to obtain an electric current in a circuit, you need a source of electrical energy (a battery or a generator) connected to both ends of the circuit. Batteries have two terminals (+ and -), which are the external part of cells where two different chemical reactions take place. Click on the following link if you wish to learn more about the inside of batteries.
The following visual shows the variation of the potential difference between the terminals of an electric battery as the light bulb consumes the energy supplied. |
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