阅读理解。
Well, somebody had to be the richest man on earth, but why did it have to be him? William Henry Gates
Bill, now just called "Bill Gates" or "Bill G". William Henry Gates was born in Seattle. In 1973, Gates entered
Harvard University as a freshman (新生). But his heart was not in his studies. After locating (定位) the
school's computer centre, he lost himself in the world of computers once again. Gates would spend many
long nights in front of the school's computer and the next days sleeping in class. So in his junior year, Gates
left Harvard to devote his energies to designing programs for personal computers, which had just entered the
marketplace. In his junior year, Gates left Harvard to devote his energies to Microsoft, a company he had
begun in 1975 with his childhood friend Paul Allen.
In 1980, the International Business Machines Corporation (IBM) chose Microsoft to develop the operating
system for its first personal computer, the PC. An operating system is a special type of program that contains
instructions for the operation of the computer. Gates devised the Microsoft Disk Operating System (MS-DOS)
for the IBM. Millions of copies of MS-DOS were sold for use in the IBM and IBM-compatible (兼容的) PC's.
Microsoft continued to grow under Gates' guidance. In 1985, the company introduced the first of a series
of PC programs called windows. These programs enable users to perform multiple (多样的) tasks through
"windows" on the computer screen and to issue (发布) commands by pointing at on screen symbols rather
than by typing instructions. Microsoft has sold milljons of copies of windows. In 1998, the United States
Justice Department, along with 20 state attorneys (律师; 代理人) general, filed an antitrust (反垄断的) lawsuit
against Microsoft. The lawsuit (案件) charged that Microsoft used unfair practices to destroy its competitors.
1. Gates ____.
A. alone set up the first software company in the world
B. began to make the personal computer with his classmate
C. founded Microsoft in 1975 by himself
D. and Allen started to set up the Microsoft in 1975
2. Which of the following words have the closest meaning with the word "devised" in the third paragraph?
A. Made.
B. Find out.
C. Developed.
D. Thought of.
3. What system did the International Business Machines Corporation (IBM) choose Microsoft to develop for
its first personal computer?
A. It was a special type of operating system that contained instructions for the computer.
B. It was a system which carried out a series of commands.
C. It was a system which performed multiple tasks through "windows" on the computer screen.
D. It was a design program.
4. Which of the following is the CORRECT order for Gates' lifetime?
a. Gates was chosen to develop the operating system.
b. An antitrust lawsuit was filed against Microsoft.
c. Microsoft introduced Windows.
d. Gates devised the MS-DOS for IBM.
A. a,b,c,d
B. a,d,c,b
C. d,c,a,b
D. b,a,d,c
的匀强磁场中，以10
的角速度匀速转动，电阻R1和R2的阻值均为50Ω，线圈的内阻忽略不计，若从图示位置开始计时，则：
上消耗的电功率为多少？
（2）
可得
,所以
上消耗的电功率为：