一只小灯泡的额定电压是8V，正常工作时通过它的电流约0.4A，现将

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问题填空题

一只小灯泡的额定电压是8V，正常工作时通过它的电流约0.4A，现将该灯泡接在20V的电源上，为使其正常发光，应______联一个______的电阻．

答案

串联电路起分压作用，所以要串联一个电阻，其阻值为：R=

20V-8V

0.4A

=30Ω；

故答案为：串，30Ω

选择题

— Have you finished reading the novel I lent you last week?

— No. I've just gone _____ the second line on Page 55. [ ]

A. as long as

B. as much as

C. as far as

D. as many as

问答题论述题

SS₄型电力机车蓄电池维护保养应注意哪些方面？