1. Apr 18, 2004

### Cernie

Hello.
I am seeking immediate help with a problem I have. Here is the problem:

A Radio Inductor. You want the current amplitude through a inductor with an inductance of 4.60 mH (part of the circuitry for a radio receiver) to be 2.20 mA when a sinusoidal voltage with an amplitude of 12.0 V is applied across the inductor.
What frequency is required?

What I tried to do was use this equation:
w = 1/(square root of(LC)) and combining it with w = I/Q which is also w0 = I/(CV), and then I would have C which I could use to find w. But that's gotta be the wrong way. I've tried some other ways which I think would make more sense, but it just doesn't seem to come out right. Is there any chance you can help me with this?
Thank you,
Cernie.

Last edited: Apr 18, 2004
2. Apr 19, 2004

### HallsofIvy

Staff Emeritus
I don't see how we can do this without knowing the frequency of the applied 12 volt current.

3. Apr 19, 2004

### chroot

Staff Emeritus
The (real) impedance of an inductor of inductance L at frequency $\omega$ is $Z = \omega L$. Ohm's law is V = IZ.

Substituting and rearranging,

$$\frac{V}{L I} = \omega$$

Solving for $\omega$, I get ~188 kHz.

- Warren

Last edited: Apr 19, 2004
4. Apr 19, 2004

### Cernie

How?

How do you get that answer?
I've already tried this method and I always get the same answer, w = 1185771 Hz = 1.19MHz.

5. Apr 19, 2004

### chroot

Staff Emeritus