## PhoenixFire 2 years ago An inductor is connected to an AC power supply with maximum output voltage $$V$$ at frequency $$f$$. What inductance is required to keep the current in the circuit less than $$I_{rms}$$? (provide minimum value) I found what inductance is needed using ${I_{rms}}=\frac{V_{max}}{2\pi f L}$ solved for L. But the question wants the minimum value, how do you find the minimum value? (Note: I have not given numbers because I don't want the question to be answered directly with numbers and no explanation)

1. kropot72

You are almost correct in your approach. However your value of L will result in the current equalling Irms, whereas the question asks for the minimum value of inductance required to keep the current less than Irms. Therefore the minimum value of inductance must be slightly greater than the value calculated by using your equation.

2. PhoenixFire

That's what I thought, but when I rounded up slightly the website still said it was wrong. $$L=0.3186$$ H so I tried 0.3187 H, and 0.32 H, all three were wrong. When I plugged those number into the equation it does result in an $$I_{rms}$$ less than the value required. Thought there may have been another explanation. I guess not... hmmm

3. Mashy

isn't Irms = Vrms/ reactance? rather than Vmax/ reactance?

4. PhoenixFire

Oh... crap! That's right. @Mashy Thank you! It was Vrms...

5. PhoenixFire

Wish I could give both of you a medal

6. Mashy

:p.. give him its ok :P