What Is Electric Potential? - Definition & Formula

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  • 0:01 Alessandro Volta
  • 1:15 What is Electric Potential?
  • 1:57 Changing Electric Potential
  • 3:22 Formula for Electric Potential
  • 4:33 Lesson Summary
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Lesson Transcript
Instructor: Maria Howard

Maria is a teacher and a learning specialist and has master's degrees in literature and education.

In this lesson, discover what electric potential is and how we measure it. Learn about the scientist Alessandro Volta and why his work led us to name a unit of measurement after him.

Alessandro Volta

Alessandro Volta wrote a letter to his buddy, Sir Joseph Banks at the Royal Society of London, in March 1800. In it, Volta drew a picture of his voltaic pile, a literal pile of 24 copper and zinc disks, plus cardboard disks soaked in salt. Volta then connected copper wires to both the top and bottom to use it as power source.

This illustration of a voltaic pile shows how it could be used as an electric power source.
Illustration of a voltaic pile

The voltaic pile and wires would then, in theory, charge something useful, like a light bulb or a small motor, but since neither existed in 1800, Volta put both wires on the tip of his tongue. His tongue, wet with saliva, was a good conductor and completed the circuit. Volta gave himself a good shock, thus proving he had made a new kind of battery, or electrochemical energy source.

While scientists now don't recommend putting live wires on your tongue, Volta was honored for his contributions to science and we named the volt (V), or the unit of measure for electric potential, in his honor. Each disk in Volta's voltaic pile created about one volt of electric potential. Since there were 24 disks, he had about 24 volts going through his tongue with each test.

What Is Electric Potential?

Electric potential is the 'push' of electricity through a circuit. It's easy to confuse electric potential with electric current, so it helps to think of electric current as the water in your shower and electric potential as the water pressure. Like water pressure, varying voltage can increase or decrease the flow of electricity.

If you turn your shower off, your water stops flowing (no more current), but your water pressure doesn't change. Just as you won't suddenly have better, or worse, water pressure when you turn your shower on again, so too does voltage remain constant for each type of energy source. A 1.5 volt battery remains 1.5 volts whether it's in use or not.

Changing Electric Potential

To take the analogy further still: Just like you can call in a handyman to help you with your water pressure problems, you can also increase or decrease voltage. Charged particles, the tiny parts of atoms that make up everything ever, don't do much on their own, but if get a bunch of charged particles together, you have quite the party. A charge collection is a group of charged particles, which together eventually form enough potential energy to serve as an energy source. I said earlier that a battery is an electrochemical energy source, which is a fancy way of saying that it gets its charge collection through a chemical reaction happening inside the battery.

The charge density ,or density of the electrons in a battery, gives the battery its voltage. If you look on the side of a household D battery, like the kind you put in a flashlight, and a small AAA battery, like the kind you put in remote control, you see that they both have a voltage of 1.5 volts. This means that despite their size difference, they have the same density of electrons within them or the same electric potential. The size difference only means that the bigger battery, D, has a longer output.

Even though these batteries are all different sizes, some of them, the D, C, AA and AAA, share the same voltage: 1.5 volts.
Photo of batteries

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