电梯为居民上下楼带来很大的便利，出于安全考虑，电梯设置了超载自动报警系统，其工作原理如图所示，电梯厢底层装有压敏电阻R1，R2为保护电阻．K为动触点，A、B为静触点，当出现超载情况吋，电铃将发出报警声_刷题宝

题干

电梯为居民上下楼带来很大的便利，出于安全考虑，电梯设置了超载自动报警系统，其工作原理如图所示，电梯厢底层装有压敏电阻R₁，R₂为保护电阻．K为动触点，A、B为静触点，当出现超载情况吋，电铃将发出报警声，电梯停止运行，下列说法正确的是（　　）

A：电梯工作时电磁铁的上端为N极

B：电磁铁磁性的强弱与电流的大小有关

C：电梯未超钱时动触点K与静触点B接触

D：电梯超载时报警说明压敏电阻的阻值随压力增大而增大

上一题下一题 0.0难度选择题更新时间:2018-07-03 06:51:17

答案(点此获取答案解析）

B

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