In an alternating current circuit, the current strength changes according to the law i = 20 sin 400 t.

In an alternating current circuit, the current strength changes according to the law i = 20 sin 400 t. What is the amplitude value of the current strength?

We have the equation:
i = 20 * sin (400 * t)
This is a classic example of writing an AC sinusoidal current equation. In general terms, this equation can be written as follows:
I = Im * sin (ωt),
where Im is the peak value of the current, ωt is the phase of the alternating current.
We correlate the given equation with the general form, we get that Im = 20 A.
Answer: the amplitude value of the current strength is 20 A.