本题目来源于试卷: Electric Currents，类别为 IB物理学
[问答题]
Driven by ac power, the same electrons pass back and forto dc;xb*b0 e8yh throug fm)r3dj: xqe9h your reading lamp over and ove 9rqe) fmdx:3jr again. Explain why the light stays lit instead of going out after the first pass of electrons.
参考答案:
There
are several factors which can be considered.
As the voltage reverses with each cycle of AC, the potential energy of
the electrons is raised again. Thus with
each “pass” through the light, the electrons lose their potential energy, and
then get it back again. Secondly, the
heating of the filament (which causes the light) does not depend on the
direction of the current, but only that a current exists, so the light occurs
as the electrons move in both directions.
Also, at 60 Hz, the current peaks 120 times per second. The small amount of time while the magnitude
of the current is small is not long enough for the hot metal filament to cool
down, so it stays lit the entire cycle.
Finally, the human eye sees anything more rapid than about 20 Hz as
continuous, even if it is not. So even
if the light was to go dim during part of the cycle, our eyes would not detect
it.
本题详细解析:
暂无
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