Unit 2 2.4.2(副本)

（视频2.4.2测试题 ）http://image.zhihuishu.com/testzhs/onlineexam/ueditor/201508/f5f24ab241db457d9bd0f6f77fa23849.jpg

<span style="font-size: 18px;（视频2.4.2测试题） http://image.zhihuishu.com/testzhs/onlineexam/ueditor/201508/18872c96b0554026a1e6fc1235022bd8.jpg</span>

<span style="font-size: 18px;（视频2.4.2测试题）</span>http://image.zhihuishu.com/testzhs/onlineexam/ueditor/201508/916291f09def4d5fa613da3244042a7d.jpg

<span style="font-size: 18px;（视频2.4.2测试题）</span>http://image.zhihuishu.com/testzhs/onlineexam/ueditor/201508/0dfad8cfefb746dda01cbfcb883e2501.jpg

2.4.2、在视频中可以看到当CD4511的消隐引脚有效时，数码管依然显示。（ ）

<span style="color: rgb(0, 0, 0); font-size: 18px;（视频2.4.2测试题&nbsp;）</span><span style="color: rgb(255, 0, 0); font-size: 18px; </span>http://image.zhihuishu.com/testzhs/onlineexam/ueditor/201508/f5f24ab241db457d9bd0f6f77fa23849.jpg

在图2．4．2所示的三极管开关电路中，已知VCC=5V，β=50，VBE=0．7V，VCES=0．2V，Rc=2kΩ。要求vI≥1．5V时，三极管工作在饱和区，试确定电阻Rb的值。

试用支路电流法或结点电压法求题2．4．2图所示电路中的各支路电流，并求三个电源的输出功率和负载电阻R。取用的功率。0．8Ω和O．4Ω分别为两个电压源的内阻。

<span style="color: rgb(255, 0, 0); font-size: 18px; background-color: rgb(255, 255, 255);<strong>&nbsp; （视频2.4.2测</strong><strong>试题）</strong></span><span style="color: rgb(255, 0, 0); font-size: 18px; background-color: rgb(255, 255, 255);</span><img width="780" height="91" src="http://image.zhihuishu.com/download/upload/uccmanage/eweb/user/20150720140135661.jpg" border="0" _ewebeditor_pa_src="http%3A%2F%2Fimage.zhihuishu.com%2Fdownload%2Fupload%2Fuccmanage%2Feweb%2Fuser%2F20150720140135661.jpg