A 25 W (P), 100 V heater (V(h)) is to be run from a (V) 250 V 50 Hz (f) sinusoidal AC supply. Calculate the inductance (L) of a suitable choke to be included in the circuit. Assume its resistance to be negligible.
P = V(h)*I*cos(alfa)
I = V/Z
Z^2 = R^2 + (2*Pi*f*L)^2
L = ? H
The Attempt at a Solution
I am basically stuck. I tried to rearrange equations to get sth, but I always end up with two unknowns, angle alfa and current I.
And I am not even sure whether I placed voltages to equations correctly.