听下面一段较长对话,回答以下小题。 (1) What is the relationship between the speakers? A . Classmates. B . Tutor and student. C . Mother and son. (2) What subject is the boy struggling with? A . Math. B . English. C . Geography. (3) What activity is related to the woman's job? A . Testing. B . Writing. C . Teaching. 答案:C
A
B(2006,杭州市)根据欧姆定律公式,可变形得到.对此,下列说法中正确的是
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A.导体电阻的大小跟导体两端的电压成正比
B.导体电阻的大小跟导体中的电流强度成反比
C.当导体两端的电压为零时,导体的电阻也为零
D.导体电阻的大小跟导体两端的电压和通过导体的电流强度无关