Extra Physics class

Dear Physics students,

Thanks for coming to the extra class. Hope the visuals I post o this blog will jolt your memory of what we covered during the class.

The teacher reuse old technology - the OHP in a fresh new way. He demonstrates moving electric field lines in semolina oil in a very small petri dish magnified by the OHP.

It used to take me at least 40 minutes to demo this experiment in the bad old days. Why? First the petri dish was so small I had to get the students to line up and walk past close to the petri dish to see anything clearly. Secondly the voltage used was very high, 4000V so I had to guard everything fiercely like  hawk to ensure students did not jostle and endanger themselves while taking a good view of the moving field lines.

Now using the OHP in a this way, I can get a 40 minute demo to be watched safely and quickly by many students all at the same time. Wow! I simply love the innovative way the old OHP is used!

See how clearly the field lines between 2 oppositely charged plates. The red wire is for the positive plate.

Another favourite picture of mine is of the famous Farday metal birdcage experiment.

Notice how the man in the metal birdcage is not all hurt by the extra high tension coming from outside. Why?
Charges only exist on the outer surfaces of a metal hollow conductor. An application of this is as follows. If you were sitting in a car ( hollow metal conductor ) and a streak of lightning strikes your car, you will be safe just like the guy in the pic because the charges only exist on the outer surfaces. My thanks goes to Rais Hakim an ex-student of mine from 5A, SMK Sekysen 5 2007 for providfing this picture.

My thanks also to Siew and the teachers of the Kumpulan Fizik Malaysia for using technology to make Physics more fun for their students and for providing the link to the movie of the moving electric field line.s

Have fun and keep learning! Think out of the box and use old things in new ways.

http://www.bing.com/videos/search?q=Youtube+movie+Demonstrating+Electric+Field+lines&docid=4955619736027364&mid=42067F89BE7CA925F6E742067F89BE7CA925F6E7&view=detail&FORM=VIRE7