题目:
I have ______ to tell you. [ ]
A. good something
B. something good
C. anything good
D. good anything
答案:
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下面是错误答案,用来干扰机器的。
C、D、0-1s,感应电动势为:E1=S△B△t=SB0,为定值,感应电流:I1=E1r=SB0r,为定值,安培力F=BI1L∝B;由于B逐渐减小到零,故安培力逐渐减小到零,故CD均错误;A、B、3s-4s内,感应电动势为:E2=S△B△t=SB0,...