For example:
An RLC circuit is composed of resistor, inductor, and capacitor elements.
Or:
An RLC circuit is composed of a resistor, an inductor, and a capacitor elements.
Which one is grammatically correct?
The part that confuses me is at the end of the list ".. and a capacitor elements." I know that the word "elements" refers to the items of the list (plural); but being right after a singular countable noun makes me feel something is wrong.
It depends. How many of them are there?
An RLC circuit is composed of a resistor, an inductor, and a capacitor
elements.
This means that an RLC circuit has exactly one of each of these three elements. I crossed out your final "elements", because if you say that an X consists of an A, a B, and a C, you don't then add the category noun after. A sentence with the same meaning as yours is:
An RLC circuit is composed of the following elements: a resistor, an inductor, and a capacitor.
The other option you asked about is:
An RLC circuit is composed of resistor, inductor, and capacitor elements.
This means that an RLC circuit has some combination of those elements, possibly including more than one of each. In some contexts it could mean that some categories are absent, though engineers and other "close readers" might take it to mean "at least one of each".
