<p> (1)当开关S闭合时,<img src="http://que-oss.fenziquan.com/web/akimg/asource/2015061915120889891.jpg">,所以稳压管截止。电压表读数U<sub>V</sub>=8.57V,而<img src="http://que-oss.fenziquan.com/web/akimg/asource/2015061915121644233.jpg"><br> (2)当开关S断开时,I<sub>A2</sub>=0,稳压管能工作于稳压区,故得电压表读数U<sub>V</sub>=12V,A<sub>1</sub>读数为<img src="http://que-oss.fenziquan.com/web/akimg/asource/2015061915122779460.jpg"><br> 计算的最后结果数字:<br> (1)U<sub>V</sub>=8.57V,I<sub>A1</sub>=I<sub>A2</sub>=4.29mA;<br> (2)U<sub>V</sub>=12V,I<sub>A1</sub>=3.6mA,I<sub>A2</sub>=0mA。</p>