一道物理题

qiuwanyingUID: 2198063

A neutral electroscope is shown above.  If a positively charged rod is brought near the knob of the electroscope, which of the following statement is true?
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A. The electroscope can be charged negatively without the positively charged rod touching the knob
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B. The electroscope can be charged positively without the positively charged rod touching the knob and using only a grounding wire
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C. The leaves of the electroscope are negatively charged

3 V- B2 S* U) }: _2 T/ m( Q" KD. The knob of the electroscope is positively charged
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E. The electroscope has a net positive charge

QuincySMUID: 2162088

我觉得木有对的阿
" T; {* C/ K3 g* v; Q' Y; M3 e. j静电感应后，knob---negative   leaves---positive   electroscope总共 0
& b& }/ {9 X9 W% z5 O) U+ V  O如果接地  相当于大地作为远端  整个验电器带负电

qiuwanyingUID: 2198063

这个……验电器不太懂耶，能不能再讲清楚点。选A

abelianUID: 2215326

用opposite attract的原理，如果rob用positively charged， 接近electroscope的話所有的negative charge 就全部吸引到knob那邊去暸， hence negatively charged。 SAT II 的一般都測試understanding the basic concept， 這個就看妳知道不知道opposite attract。