The period T with which the current at the wall socket changes is 0.017 s.
It also ranges from 0.155 s to 0.0189 s since the cycles is not given in the question.
Explanation:
The current reaches 3.8 A once for every cycle. So there must have been 10 cycles (10 periods) in 0.17 s.
Using 'T' for period:
10 T = 0.17
T = 0.17 / 10
T = 0.017 s.
The question doesn't tell about the cycles and so we assume it as 10 cycles. If there are 9 cycles due to the current 3.8 A at the exact beginning and end of 0.17 s. This would make the period T as
0.17 / 9 = 0.0189 s approx.
Likewise, if the 3.8 A occurs at the end of the 1st cycle, 11 cycles would have passed during 0.17 s.
In that case the period = 0.17 / 11 = 0.155 s approx.
So T could be in the range from 0.155 s to 0.0189 s.
