click here for a guide to creating quizzes in Google Forms). In both of those cases you may have a need to limit the number of responses, limit the length of responses, or set a cut-off time at which the form will stop accepting responses. While you can simply click "stop accepting responses" in your Google Form, you do have to remember to do it. FormLimiter solves that problem and two others.
FormLimiter is a script that you can install in the Google Spreadsheet in which you are collecting responses from a Google Form. The script allows you to limit the number of responses to a form, limit the number of characters in a response, and set a time at which the form will automatically stop accepting responses. The images below will walk you through the process of installing FormLimiter. (Click the images to view them in full size).