超星 - 第二单元作业 - 查题吧

单选题

The hospital bought X-ray machine day before yesterday.

A. an / the
B. the / an
C. a / the
D. an / a

单选题

It is a great way to show our thanks the end of the year.

A. to
B. by
C. toward
D. for

单选题

The staff wore hats all week and tipped them toward the volunteers we saw them.

A. as
B. before
C. after
D. at

单选题

During National Volunteer Week we recognized our volunteers taking them to the movies.

A. with
B. to
C. by
D. at

单选题

I just heard awful news from my son that our dog climbed your backyard.

A. a / to
B. an / by
C. the / to
D. the / into

单选题

在纯电容电路中,电压有效值不变,频率增大时,电路中电流将( )题

A. 增大
B. 减小
C. 不变
D. 无法判断

单选题

一个电热器接在10V的直流电源上,产生的功率为P。把它改接在正弦交流电源上,使其产生的功率为P,则正弦交流电源电压的最大值为( )

A. 7.07V
B. 5V
C. 14.1V
D. 10V

单选题

我国工业电力网的供电频率为50Hz,则对应的角频率为()

A. 314rad/s
B. 628rad/s
C. 100rad/s
D. 141rad/s

单选题

串联电路的谐振条件是()。

A. XL>XC
B. XL=XC
C. XL<XC
D. XL=R

单选题

在纯电容电路中C=50μF,工频电流的频率ƒ=50HZ,则该电容的电抗为：

A. 50Ω
B. 2500Ω
C. 400Ω
D. 64Ω

8