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DC Circuits (id: b666f1381)

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admin 发表于 前天 08:26 | 显示全部楼层 |阅读模式
本题目来源于试卷: DC Circuits,类别为 IB物理学

[问答题]
Explain why birds ca:jcgdza+e ,f9bl)wgw )x bvh,8 c*a+so(, bw zn sit y,y3 4nw. .w-g xjgypvon power lines safely, whereas leaning a metal ladder up agai w.-,y3npy.w4x ygvjgnst a power line to fetch a stuck kite is extremely dangerous.




参考答案:
The birds are safe because they are not grounded.  Both of their legs are essentially at the same voltage (the only difference being due to the small resistance of the wire between their feet), and so there is no current flow through their bodies since the potential difference across their legs is very small.  If you lean a metal ladder against the power line, you are making essentially a short circuit from the high potential wire to the low potential ground.  A large current will flow at least momentarily, and that large current will be very dangerous to anybody touching the ladder.


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