I have to recommend TV set dissection as a great activity to review physics concepts in electricity and magnetism. It's great fun! Just keep your eyes out for old clunkers at garage sales - bring them to class, and let the fun begin! My students are required to identify as many electrical components as possible, and then create a display that outlines the functions of the parts.
Actually, the older the set, the more interesting they are inside! TV sets that are sold now have the electrical components miniaturized to the extreme. A couple of words of caution... never open up the case of a TV set that has been recently been powered up - you can be killed by electrical shock. The clunkers we tear apart have been sitting for at least six months. Opening a set that has been recently powered up should only be done by a qualified electrician. You should also be very careful with the picture tube - it's a vacuum tube, so dropping it will produce an implosion that will send sharp shards of glass flying. Take care!!!
This is a great activity for reviewing electrical components and gives students insight into how those components are actually put into use. If you'd like to take it a step further, you can also use the opportunity to investigate the picture tube!
Physics teachers talk about the vacuums and electron guns, but students never seem to get to experience and see them first hand. Or do they? Well, we did, and the whole thing worked out great! Check out the following QuickTime movie (944k) that illustrates the last steps of removing the electromagnetic yoke from the picture tube, and snapping the glass nipple at the back of the set so that students can hear the air rushing in as it violates the vacuum of the tube;
This type of activity must be only done with older students - it has several dangerous aspects to it, so students need to exercise a great deal of responsibility. Eye protection is a must, and workgloves are probably a good idea when snapping the glass. Don't ever drop a picture tube or rest it on the long, slender portion. You want to avoid shattering it - glass will fly dangerously everywhere (and the inside surface of the front of the tube has poisonous phosphor - yuck)! Also be very careful removing the yoke and the circuit board and plastic from the end of the tube when you are trying to get at the nipple - take your time, be gentle - you don't want the glass to be broken unexpectedly.
Once you've got the vacuum of the tube violated, you can now gently tap off the end of the tube and extract the electron gun - cool!
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