I wan't to write the instantaneous value expression from the curves below.

The voltage is the bigger one and the other is the current and the scale for the voltage is 1 V and 10 mA for the current.

f = 1/(20E-3) = 50 Hz

For the voltage I get |U| = 2 V and α = 0° => u(t) = 2 Sin (2π50t) V

For the current I get |I| 10 mA and from the graphs it looks like the current is ~1,25 ms behind so I get α =(-1,25/20)*360 = -21,6° => i(t) = 10 Sin(2π50t - 21,6°) mA

The awnser for the current is wrong and it should be 10 Sin(2π50t - 30°) mA. What am I doing wrong when calculating the phase shift?

http://s32.postimg.org/yhmu67ryd/moment.png

The voltage is the bigger one and the other is the current and the scale for the voltage is 1 V and 10 mA for the current.

f = 1/(20E-3) = 50 Hz

For the voltage I get |U| = 2 V and α = 0° => u(t) = 2 Sin (2π50t) V

For the current I get |I| 10 mA and from the graphs it looks like the current is ~1,25 ms behind so I get α =(-1,25/20)*360 = -21,6° => i(t) = 10 Sin(2π50t - 21,6°) mA

The awnser for the current is wrong and it should be 10 Sin(2π50t - 30°) mA. What am I doing wrong when calculating the phase shift?

http://s32.postimg.org/yhmu67ryd/moment.png