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seen Nov 13 '12 at 4:19

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Nov
14
answered What is the difference between a white object and a mirror?
Nov
14
answered What's the difference between dim and bright light?
Nov
13
comment Desperately Need Help with Grade 9 Static Electricity
In these situations, you have at least two approaches with your grade nine class: 1) do not show them the foil interacting with the screw, since you can't explain it to your own satisfaction, and 2) show them the interaction, and tell them you don't know why it works that way. I would go with option 2: you might just have someone in the class who CAN explain it (a), and (b) you might just inspire someone to go into the sciences, because the excitement of science lies in exploring new things and in seeking explanations based on what we already know.
Nov
13
comment Alternate layman's metaphors for illustrating curved space-time
@Lub, it's a different question, and I think your 2nd comment should be added as an answer.
Nov
13
comment Alternate layman's metaphors for illustrating curved space-time
Could you provide a citation that explains the distinction between intrinsic and extrinsic curvature as it relates to gravitation? I'm having difficulty accepting that the curvature of a bent piece of paper is zero.
Nov
13
comment Desperately Need Help with Grade 9 Static Electricity
Hmm, very curious. I must try this experiment for myself!
Nov
13
comment Desperately Need Help with Grade 9 Static Electricity
In any case, it's a good idea not to accept answers right away anyway, to encourage answers from others first.Cheers, JB
Nov
13
comment Desperately Need Help with Grade 9 Static Electricity
To your second objection, if the inside of the PVC is negatively charged, the tip of the screw, being on the inside of the pipe, would be induced positively as well. You can test the charging of the inside of the pipe with your negatively charged foil.
Nov
13
comment Desperately Need Help with Grade 9 Static Electricity
To your first objection, with induced charges, the forces depend not only on the amount of charge but also on the spatial variability of the force (the force is proportional to the gradient of the electric field). The smallness of the screw compared to the size of the pipe means there will be large forces present.
Nov
13
answered Desperately Need Help with Grade 9 Static Electricity
Nov
11
comment What are the specific requirements for a do-it-yourself quantum double-slit experiment?
Young's slit experiment as described in the videos with ordinary light can be explained classically using interference of waves. It's a good question though how to do the quantum version of it using single particles at home. I wonder about using a cooled CCD capable of single photon detection (maybe an EMCCD) looking at a faint astronomical source through a telescope. If you can show a time-lapse movie of the build-up of the image, one photon at a time, you'd be demonstrating the quantum nature of light.
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24
answered How to place a mirror parallel to a wall?
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asked What is the most energy efficient way to boil an egg?
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revised Can Maxwell's equations be derived from Coulomb's Law and Special Relativity?
Changed displacement current to LaTeX form.
Feb
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answered Can Maxwell's equations be derived from Coulomb's Law and Special Relativity?