当已知避雷针的高度A采用30时,按有关计算式计算出避雷针在地面上的保护半径r是()。A.25m;B.35m;C.45m;D.52m。

作者: rantiku 人气: - 评论: 0
问题 当已知避雷针的高度A采用30时,按有关计算式计算出避雷针在地面上的保护半径r是()。
选项 A.25m; B.35m; C.45m; D.52m。
答案 C
解析

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