The current, voltage and electromotive force calculated by AC circuit are all calculated by effective value, and their effective value is equal to the maximum value of the corresponding quantity multiplied by half of the root number 2!

Because u =10 sin (wt+pi/2) v.

Maximum voltage Um= 10.

1。 Find the module of z

Z = sqrt (400 2+700 2) = 806 ohms

The maximum current is: I = 10/806 = 0.05438+02 A.

So the current is: I = 0.707 * 0.012 = 0.0085a.