I my opinion Donald's questions (see below) can become a mental trap. For
some reason they remined me the proverbial "Have you stoped beating your
wife" question. Or "predict which side of the image will disappear when the
left side of this lens is covered". A student who remebers that real images
are inverted will think that the purpose is to test him on this. And his
answer will be "wrong".
People who ask would usually phrase the question more carfully but this
may not be enough to prevent generating a response to a different question.
Don's pair of questions can be very useful; but it can also become a
mental trap.
Ludwik Kowalski
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This is not a problem for you folk, but one to try on your *students* to
see whether they grasp the capacitor concept.
1. A capacitor is charged with 6 microcoulomb, and the potental of the
capacitor is measured. It is 3 volt. What is its capacitance?
2. This same capacitor is now carefully discharged completely. What is its
capacitance now?
-- Donald
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