Q1: The frequency of the AC mains in the European countries 50 (Hz) and the effective value of the voltage is 220 (V). Due to turbine control disruption of one the power generation facility the frequency was fluctuating; calculate the period of the waveform when the frequency is (5.15x10^1) (Hz). Enter the answer in seconds (s) rounded to 3 significant digits.

* so I did P = 1/f = 1/51.5Hz = 0.194s which was wrong

* the program they're using for online quizzes requires these types of answers to be in scientific notation for some reason, so I put 1.94x10^-1

Q2: Calculate the instantaneous value at t=(1.0400x10^1) (ms) of the current in a heating element connected to (1.000x10^2) (V) 60.0 (Hz) AC mains. The resistance of the heater is R=(2.50x10^1) (Ω) Enter the answer in Amperes rounded to 3 significant digits.

* I tried calculating the instantaneous voltage first: v=Vmsin(2*pi*f*t) = 100 sin (2*pi*60*10.4ms) = 6.84V

* Then divided by resistance to get current = *ans / 25 = 274 mA = 2.74x10^-1A

Q3:

Calculate the angle (θ) (in degrees) of the complex number

- (8.2000x10^0) - j (2.70x10^0).

Enter the answer rounded to three significant digits.

* I tried doing θ = tan-1(y/x) = tan-1(-2.7/-8.2) = 18.2

* Then I added 270 since it should be in the fourth quadrant: ans + 270 = 288.23 = 2.88x10^2

If someone could tell me what I'm doing wrong that would be great, thanks!

I've tried this homework 3 times, and each time I got these same 3 answers wrong.