Question

when do you place a comma after a dependent clause

Answer 1

When you want to use commas and semicolons in sentences and when you are concerned about whether a sentence is or is not a fragment, a good way to start is to be able to recognize dependent and independent clauses. The definitions offered here will help you with this.

Independent Clause

An independent clause is a group of words that contains a subject and verb and expresses a complete thought. An independent clause is a sentence.

Jim studied in the Sweet Shop for his chemistry quiz.
Dependent Clause

A dependent clause is a group of words that contains a subject and verb but does not express a complete thought. A dependent clause cannot be a sentence. Often a dependent clause is marked by a dependent marker word.

When Jim studied in the Sweet Shop for his chemistry quiz . . . (What happened when he studied? The thought is incomplete.)
Dependent Marker Word

A dependent marker word is a word added to the beginning of an independent clause that makes it into a dependent clause.

When Jim studied in the Sweet Shop for his chemistry quiz, it was very noisy.
Some common dependent markers are: after, although, as, as if, because, before, even if, even though, if, in order to, since, though, unless, until, whatever, when, whenever, whether, and while.