The passive voice is frowned upon by many teachers. Or should I say, many teachers frown upon the passive voice? Today's sites illustrate the differences between active and passive voice, bust some common grammar myths, and will help you write with more clarity.
"Elements of Style" by William Strunk, Jr. and E.B. White is one of my favorite books on writing. This online edition is the one Strunk published privately in 1918 as a Cornell professor. In 1959, White (one of Strunk's students) revised it and re-published it as a co-author. Of interest today is item eleven, which teaches us although the passive voice is called for in some situations, the "habitual use of the active voice makes for forcible writing."
The Guide to Grammar and Writing gives us detailed examples of the passive voice. For example, only verbs that take objects, known as transitive verbs, can be used in passive voice. Be sure to take the quiz (link at the bottom of the page) on revising passive constructions. "WARNING! Some of these sentences do not use passive verbs or are better off left in the passive, so this exercise will also engage your attention in recognizing passive constructions and in using them when appropriate."
This seven-section resource from OWL at Purdue University has a table of contents at the bottom of every page. To print all seven sections at once, click on the Full Resource for Printing button in the green nav bar just below the Summary. This lesson offers illustrated examples of active voice, showing you the subject acting upon the object (arrow points to the right) versus the passive voice, where the arrow from the object points to the subject on the left. My favorite click is the Further Suggestions section which offers tips such as "Avoid starting a sentence in active voice and then shifting to passive."
This auto-correcting quiz from the Study Zone at University of Victoria provides ten opportunities to change sentences from active to passive, and vice a versa. If you are stuck, the computer offers correct answers (just click the "Show Me" link.) Of course, there's always more than one correct way to structure a sentence, so just use the computer answer as an example. The quiz sentences are from a common urban legend called the Choking Dog you can read here
This handout from the University of North Carolina Writing starts out by busting common passive voice myths. Here are a few. "Use of the passive voice constitutes a grammatical error." "Any use of "to be" (in any form) constitutes the passive voice." Great stuff! There is also an important section on the use of passive voice in Scientific Writing. "The rationale for using the passive voice in scientific writing is that it achieves â€˜an objective tone' â€“ for example, by avoiding the first person."