Using Copyrighted Material in Your Assignments
You do not require the permission of a copyright owner to copy a substantial amount of a work in order to support or illustrate a point or argument you are advancing in your work. There is a requirement to identify and cite your source.
Your use of the work would be limited to the portion required to illustrate your point and wouldn't normally include reproducing the entire work. There are sometimes instances where the entire work must be used when using just a portion does not support your argument fully (photographs are just one example where it requires the whole photo to be used, and not just a portion of it).
What about multimedia?
There's a provision in the Copyright Act that provides for the use of copyright protected audio and video in multimedia assignments. The Non-commercial user generated content provision now permits posting such presentations/assignments to the Internet on sites such as Vimeo and YouTube.
A note on substantiality
Under current copyright law the copying of a substantial portion of a work is covered by copyright. An insubstantial amount is always available to use with permission without fear of copyright infringement. There is no definition within the Copyright Act of what constitutes substantial or insubstantial. It's a judgement call that takes into account both quantity and quality. Commonly thought of examples of insubstantial uses include quotations from a work, a table, graph or figure or short clips from an audiovisual work.