Daniel B. answered 10/31/20
A retired computer professional to teach math, physics
My choice is A for the following reason.
The voltage will have a general form of Asin(kt + p).
1) The amplitude, A, is the maximum voltage, which is given as 12 V.
2) The constant k is computed from the given frequency of 80Hz.
That implies period of 1000/80 = 12.5 ms.
That means that when t = 12.5, kt = 2π(which is the period of sin).
k = 2π/12.5
3) The phase p is not mentioned in the problem, so
the most reasonable choice is p = 0.
Thus we need to evaluate the resulting function at t = 10ms:
12sin(2π10/12.5) = -11.4