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What is electric charge?

In my quest to understand computing and networking, I have admitted a need to learn electronics. There’s no escaping it any more.

So let’s start with a basic concept: “electric charge” (denoted q). The electric charge of an object is basically its number of electrons. More precisely, it is its number of electrons minus its number of protons. If you think of electrons as debt and protons as credit, the charge of something is its “electron debt”. Thus we say an object has “negative charge” if it has an excess of electrons compared to protons, and we say it has “positive charge” if it has less electrons than protons.

The proper unit of charge is the charge held by one proton, called the “elementary charge”, and denoted e. Thus a proton has a charge of 1e, an electron has a charge of -1e, an ion has some positive integer e, an ordinary uncharge object has a charge of approximately 0e, and so on.

Unfortunately we don’t usually measure charge in electron debt. Instead we measure it in “Coulombs”, but there’s an easy conversion: 1 Coulomb = around 6,240,000,000,000,000,000 e. Conversely, Negative 1 Coulomb is -6,240,000,000,000,000,000 e.

The Coulomb makes it less clear is that charge is an integer and that it derives from number of electrons. Something cannot have 1.5 electrons of charge.

What can computers do? What are the limits of mathematics? And just how busy can a busy beaver be? This year, I’m writing Busy Beavers, a unique interactive book on computability theory. You and I will take a practical and modern approach to answering these questions — or at least learning why some questions are unanswerable!

It’s only $19, and you can get 50% off if you find the discount code ... Not quite. Hackers use the console!

After months of secret toil, I and Andrew Carr released Everyday Data Science, a unique interactive online course! You’ll make the perfect glass of lemonade using Thompson sampling. You’ll lose weight with differential equations. And you might just qualify for the Olympics with a bit of statistics!

It’s $29, but you can get 50% off if you find the discount code ... Not quite. Hackers use the console!

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