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Question Video: Identifying the Unit Symbol for Coulombs Science

Which of the following is the correct unit symbol for coulombs? [A] Q [B] O [C] c [D] q [E] C

02:53

Video Transcript

Which of the following is the correct unit symbol for coulombs? Is it (A) uppercase Q, (B) uppercase O, (C) lowercase c, (D) lowercase q, or (E) uppercase C?

Let’s recall that the coulomb is the standard SI unit for electric charge. And we know that SI units follow certain rules to help us communicate quantities in a universal way. When we talk about electric charge, we might remember that the letter 𝑄 is often used to represent an amount of charge. For instance, we might express the charge of an object by saying 𝑄 is equal to four coulombs. But an amount of electric charge is not the same thing as the unit we use to measure charge. So while 𝑄 can be used to symbolize a charge value, it is not used to symbolize the actual units of coulombs. Because of this, we should eliminate answer choices (A) and (D).

Now, one thing that’s easy to remember about the unit of coulombs is that the unit symbol begins with the first letter of the word coulomb. Therefore, we know that O isn’t the correct symbol, so we can eliminate answer choice (B) as well. Now it’s just up to us to recall whether the unit symbol is a lowercase or uppercase C.

We might recall that the coulomb was named after the physicist who made important discoveries about electricity. It turns out that there are specific rules about how to express SI units that were named after people. One rule is when we write out the entire name of a unit, like the whole word coulombs, we don’t need to use a capital letter. This is because we’re technically referring to the unit, not the actual person who the unit is named after.

But don’t be fooled by answer choice (C). Remember that this question is specifically asking us about the unit symbol for coulombs. There is another rule that SI units named after people must be symbolized by a capital letter. This means that the unit symbol for coulombs is capital or uppercase C. Therefore, (E) is the correct answer. The correct unit symbol for coulombs is capital C.

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