搜题请搜索小程序“爱下问搜题”
问题 计算题

如图所示的电路中，电源的电动势E=12V，内阻未知，R1=8Ω，R2=1.5Ω，L为规格“3V，3W”的灯泡，开关S断开时，灯泡恰好正常发光．（不考虑温度对灯泡电阻的影响）试求：

（1）灯泡的额定电流和和灯丝电阻；

（2）电源的内阻；

（3）开关S闭合时，灯泡实际消耗的功率．

答案

（1）3Ω   （2） 1Ω   （3）0.48W

题目分析：（1）灯泡的额定电流      1分

灯丝电阻     1分

（2）断开S时，灯L正常发光，即I1=I0，根据闭合电路欧姆定律

          2分

得         1分

（3）闭合S时，设外电路总电阻为R外

       2分

设干路电流为I总          1分

灯两端的电压UL          1分

灯的实际功率PL：         1分

单项选择题

Colleges in the US have added a new subject, “great chemistry”, to their curriculum today. “Green chemistry (53) how we can develop products that won’t (54) the environment,” explains Paul Anastas, director of Yale University’s Center for Green Chemistry and Green Engineering, opened at the beginning of this year. The American Chemical Society, (55) approves more than 600 college chemistry programs, only lists about a dozen that teach green chemistry. But that (56) is growing.
Cambridge College in Massachusetts is offering “ an introduction to green chemistry” course this gall and is offering the nation’s first bachelor’s and master’s (57) in green chemistry. The program will have classes in environmental science and even environmental (58) and policy. These subjects are not (59) taught to chemistry major.
Employers (60) the introduction of green chemistry. Businesses are increasing seeking graduates (61) backgrounds in the subject because it can help them make or save money in he development and manufacturing of products. “We need people who can not only understand their place (62) , but also understand the worldwide perspective,” said Adam Peterson, a chemical division manager at Dow Corning Corp.

A．controversially
B．eventually
C．gradually
D．traditionally
查看答案
单项选择题

已知小写字母a的ASCII码为97，大写字母A的ASCII码为65，以下程序的结果是 ______。main(){unsigned int a=32,b=66；printf("%c\n",a｜B) ;}

A．66

B．98

C．b

D．B
查看答案