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.