【简答题】![](https://cos-cdn.shuashuati.com/shuashuati-web/2024-0521-0905-00/logo-new-ad743.png)
在测量金属丝电阻率的试验中,可供选用的器材如下: 待测金属丝:Rx(阻值约4Ω,额定电流约0.5A); 电压表:V(量程3V,内阻约3kΩ): 电流表:A1,(量程0.6A,内阻约0.2Ω); A2(量程3A,内阻约0.05Ω): 电源:E1(电动势3V,内阻不计) E2(电动势12V,内阻不计) 滑动变阻器:R(最大阻值约20Ω) 螺旋测微器;毫米刻度尺;开关S;导线。 ①用螺旋测微器测量金属丝的直径,示数如图所示,读数为______mm。
②若滑动变阻器采用限流接法,为使测量尽量精确,电流表应选______、电源应选______(均填器材代号),画出电路原理图。
![](data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACAAAAAgCAYAAABzenr0AAAA5ElEQVRYR2NkGGDAOMD2M+B0wKpVq9huv/jbxPD/fxwDA4MkhQ59zsDIuEhVgrkuLCzsF7JZOB3QOml5B8P//+UUWoyqnZGxszovsoI4B0xc9gyfzxmZmb2rcsK3IRvWMWm599///7fgcfTz6vwoKWId8B+f75kZGX0q8iK3kugAhur8KJRQxx0FE5fhdQC5UTPqgNEQGA2B0RAYDYHREBgNgaETAuTW96TqG7yt4tbRFhGRIQBqHTP9+8dIoDUMTxqk5AK8zXKYiaDWMYhNpANIaJYPdMdkwLtmpOZnctUPeDkAAP6tmiH1ggTLAAAAAElFTkSuQmCC)
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