问题 填空题

如图所示,仪器中常用两个阻值不同的可变电阻来调节电路中的电流,一个作粗调(明显改变电流的大小)一个作细调(稍微改变电流的大小).已知R1>R2,则图(a)中用作粗调的是______,图(b)中用作粗调的是______.(填“R1”或“R2”)

答案

在(a)电路中,由于是串联电路且R1>R2,据欧姆定律I=

U
R
知,在电压一定的情况下,电阻变化大的对电路中的电流影响就大,故R1对电流的影响大,起粗略调节作用;在(b)电路中,由于是并联,即其并联的电阻起到分担电流的作用,据欧姆定律I=
U
R
知,在电压一定的情况下,电阻的变化越小,其对干路电流的影响就越大,故R2对电流的影响大,起粗略调节作用.

故答案为:R1;R2

阅读理解

阅读理解。

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