【单选题】电路如下图所示,是一种光电报警电路的一部分。三极管 T 的放大倍数β =100 ,基极和发射极的正向压降为 0.7V ;电阻 R 1 =6kΩ , R 2 =1kΩ ;蜂鸣器是阻性元件,且电阻为 100 Ω;当流过发光二极管的电流大于等于2mA时,发光二极管就会发光;当流过蜂鸣器的电流大于等于 60mA 时,蜂鸣器就会鸣叫;电压 U CC =12V 。在正常情况下, B 点电位为 0V 。若 B ...
【单选题】代码填空【使用递归实现二分查找】 int binarySearch(int a[], int key, int low, int high) { if (low > high) return -1; int mid; mid = (low + high) / 2; if (key == a[mid]) return mid; else if (key < a[mid]) return _____...
【简答题】(1)在图4-6所示电路中,调整元件是 ,比较放大管是 。提供基准电压的元器件是 和稳压管 Vz 。 (A.放大器A B.三极管VT C. D. E. F. ) (2)在题图中,R 2 的滑动触点向上移,输出电压Uo( )。 A 、降低 B、提高 C、无影响 D、变化因元件参数而不同 (3)在题图中,Uo升高,会引起U b ( )。 A 、降低 ...
【简答题】In the 1950s, classroom violence ________. A) was something unheard of B) was by no means a rare occurrence C) attracted a lot of pubic attention D) began to appear in ysts’ data
【单选题】A psychological issue that began to be discussed in the 1950s was the question of the most appropriate age for second language learning. The ability of young children to learn language 'easily' had, f...