The current in an alternating circuit varies in intensity with time. If I represents the intensity of the current and t represents time, then the relationship between I and t is given by
?
I = 20cos 160?t
?
where I is measured in amperes and t is measured in seconds. Find the maximum value of I and the time it takes for I to go through one complete cycle.
?
A. The maximum value of I is 40 amperes; one complete cycle takes 
seconds.
B. The maximum value of I is 5 amperes; one complete cycle takes 
seconds.
C. The maximum value of I is 20 amperes; one complete cycle takes 
seconds.
D. The maximum value of I is 40 amperes; one complete cycle takes 
seconds.
E. The maximum value of I is 20 amperes; one complete cycle takes 
seconds.
Answer: E
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