Homework Help: Inductance Question

1. Mar 23, 2005

z_sharp

Hi all, I've managed to solve the following question but the answer I'm getting doesn't seem right...

What inductance must be connected to a 17 pF capacitor in an oscillator capable of generating 550 nm (i.e. visible) electromagnetic waves? Comment on your answer.

To solve it I just rearranged the following equation and isolated L

$$f=\frac{1}{2\pi\sqrt{LC}}$$

I'm also not sure what the prefix 'p' in the 17pF stands for...

Thanks

Last edited: Mar 23, 2005
2. Mar 23, 2005

whozum

p stands for pico, which is equivalent to 10^(-12).

3. Mar 23, 2005

z_sharp

So this is what I have now, the answer I'm getting is extremly small, could someone please just check over my work to see if I have made any errors... Thanks

$$\begin{gather*} C=17pF=1.7\times10^{-11}F\\ \lambda=550nm=5.5\times10^{-7}m\\ c=3.0\times10^8m/s \end{gather8}$$

$$\begin{gather*} f=\frac{1}{2\pi\sqrt{LC}\\ \frac{c}{\lambda}\sqrt{LC}=\frac{1}{2\pi}}\\ LC=(\frac{\lambda}{2c\pi})^2\\ L=(\frac{\lambda}{2c\pi})^{2}(\frac{1}{C})\\ L=5.0\times10^{-21}\\ \end{gather*}$$

4. Mar 23, 2005

whozum

Your algebra looks right to me. I don't remember much about inductance to comment on the physics of it.