The term ‘polarity’ refers to opposite poles, or contradictory tendencies. We could if we liked write about polarity in American politics. However, we will discuss what polarity means in electrical terms.In the energy industry, we use electrical polarity to refer to positive and negative electrical potential at either end of a circuit.
Electrical Polarity in Batteries
In batteries, the terminals are where negative and positive circuit endings attach. Early engineers may have chosen the term because the opposite ends of bus routes and railway lines are terminal stations. But it’s not really that important.
Conventional electrical polarity has direct battery current flowing through the circuit from the positive to the negative terminal. While electrons flow in the opposite direction inside the battery simultaneously.
This is different in the case of alternating electric current though, because the chemical reaction is more complex. In this case, the two terminals exchange electrical polarity many times a second. While the electron flow changes direction less frequently.
How to Identify the Poles in Batteries
Batteries are direct current devices. They have to be, or else the alternating cycles would cancel each other out meaning average voltage would always be zero. The positive terminal is marked red, or with a plus, or both.
The negative terminal on the other hand is black, or marked negative, or both. Positive terminals of car batteries are often slightly fatter. This has nothing to do with electrical polarity though. The intention is to avoid connecting them the wrong way around.
Modern cars usually earth the negative terminal to the chassis. However, some older vehicles may have positive earths. It is essential not to confuse the two, because this could severely damage both the battery and the electrical system. If in doubt about electrical polarity, please google it first. It is simply not worth taking a chance.
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Bridging Across from Direct to Alternating Current
Preview Image: Mercury Battery
