please answer the following circuits question...........thank you?

Question

Calculate the current that flows in a 150mH inductor connected to a 100v, 250 Hz supply.

Show work

Answer 1

The current can be calculated from I = V/Z where Z is the impedance of the inductor. The impedance (in ohms) is equal to (ignoring the phase difference) 2*pi*f*L, where f is frequency and L is the inductance.

So, Z = 2*pi*250*0.150 = 75*pi ohms.

Then, I = V/Z = 100/(75*pi) = 0.42 amperes. of course, this is 90 degrees out of phase with the voltage.

Answer 2

First, we need the Inductive reactance that this inductor gives, which depends on the frequency of supply. Are you sure it's 250 hz? usual supply freq's go around 50~60 hz.. whatever, let's stick to 250.
reactance, X = 2 * pi * f * L = 2 * 3.1416 * 250 * 150/1000
gives X = 235.62 Ohms. (note, this is not resistance, but reactance)

Total impedance of the circuit, Z = X = 235.62 (there's no other resistance etc, rite?)

finally, Current I = V / Z
I = 100 / 235.62 = 0.4244 Amps
and that's your current. savvy?
(note: this current is gonna LAG the voltage by 90 degrees, 'coz it's a purely inductive circuit)