广东的春季,天气潮湿,需要除湿,如图1所示为某实验室的自动除湿器。除湿器内部的电路结构由控制电路和工作电路两部分组成,简化后的电路图如图2所示。控制电路中的电源电压
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmsub%3E%3Cmrow%3E%3Cmi+mathvariant%3D%22normal%22%3EU%3C%2Fmi%3E%3C%2Fmrow%3E%3Cmrow%3E%3Cmn%3E1%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmsub%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmn%3E12%3C%2Fmn%3E%3Cmi+mathvariant%3D%22normal%22%3EV%3C%2Fmi%3E%3C%2Fmath%3E)
, 调控电阻
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmsub%3E%3Cmrow%3E%3Cmi+mathvariant%3D%22normal%22%3ER%3C%2Fmi%3E%3C%2Fmrow%3E%3Cmrow%3E%3Cmn%3E0%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmsub%3E%3C%2Fmath%3E)
的阻值范围为
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmn%3E0%3C%2Fmn%3E%3Cmo%3E-%3C%2Fmo%3E%3Cmn%3E1000%3C%2Fmn%3E%3Cmi+mathvariant%3D%22normal%22%3E%CE%A9%3C%2Fmi%3E%3C%2Fmath%3E)
, R为装在除湿器内的湿敏电阻,其阻值随相对湿度
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi+mathvariant%3D%22normal%22%3E%CF%86%3C%2Fmi%3E%3Cmo%3E%28%3C%2Fmo%3E%3C%2Fmath%3E)
空气中含有水蒸气的百分比,单位为:
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi+mathvariant%3D%22normal%22%3E%25%3C%2Fmi%3E%3Cmi+mathvariant%3D%22normal%22%3ER%3C%2Fmi%3E%3Cmi+mathvariant%3D%22normal%22%3EH%3C%2Fmi%3E%3Cmo%3E%29%3C%2Fmo%3E%3C%2Fmath%3E)
变化的图像如图3所示。L为磁控开关,当湿敏电阻R的阻值发生变化时,控制电路中的电流随之发生变化,当电流大于或等于20mA时,L的两个由磁性材料制成的弹片具有了磁性并相互吸合,工作电路的压缩机开始带动系统进行除湿。工作电路两端电压
![](https://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmsub%3E%3Cmrow%3E%3Cmi+mathvariant%3D%22normal%22%3EU%3C%2Fmi%3E%3C%2Fmrow%3E%3Cmrow%3E%3Cmn%3E2%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmsub%3E%3Cmo%3E%3D%3C%2Fmo%3E%3Cmn%3E220%3C%2Fmn%3E%3Cmi+mathvariant%3D%22normal%22%3EV%3C%2Fmi%3E%3C%2Fmath%3E)
, Rg为保护电阻,磁控开关L的线电阻不计。问:
![](http://tikupic.21cnjy.com/2024/01/11/95/fc/95fc22dfa1df9d89969f7bddc9a14682.png)