Recent content by Blastrix91

Great. Yeah, that was clear. I'm grateful ^^

Homework Statement When deriving the intensity of an electromagnetic wave in my textbook, there was a part I didn't quite get. It's how I = Watts/m^2 becomes I= u c My textbook gave an example of a electromagnetic wave through a cylinder, with cross-section area A. In 1 second it would...

Ah now I get it. I guess what confused me was that it was called an approximation, but as you pointed out the small x wasn't going towards zero. Thank you both of you ^^

So there are no approximation calculations behind? (Like a Taylor approximation or something?)

Homework Statement I just stumbled upon an approximation I don't get where comes from Homework Equations F(x+dx) -F(x) = dF/dx dx The Attempt at a Solution My textbook just stated it out of nothing, so I have no idea where to start.

^It did thank you for posting them. That was some pretty neat examples :b

hmm thanks. I might have gotten it (tried surfing around the web) I do get this though: \oint\limits_S \vec{B} \cdot d \vec{A} = 0 So that helped a lot But from my understanding of what divergence is, I don't quite get it when it is in the form: div B = 0 (with my understanding of...

When you say div B = 0 mean that magnetic field lines only forms closed loops, is that in the moment a magnetic field begins and end (if that were to happen) there would be a change in what goes in in relation to what goes out and thus div B wouldn't be 0? That at least makes sense to me. The B...

The divergence of a vector field tells us how many field lines goes into a volume element in relation to how many goes out. So if div B = 0 there should be the same amount of magnetic field lines going into a volume element as are going out of it right? But the Biot-Savart equations tells...

All three things you pointed out gave me the right answer. Thank you ^^

Homework Statement http://img809.imageshack.us/img809/5676/unavngivetk.png Additional table info: The molarmass ##M_{air}## is ##29 * 10^{-3} g/mol = 29*\frac{10^{-3}}{1000} kg/mol## The mass density ## \rho_{air} ## is ##1.3 kg/m^{3}## The dielectric constant ## K_{air}## is 1.00059 My...

Homework Statement I'm having some troubles with my calculus. I can't get from the first step to the second step in the example below: Homework Equations http://img853.imageshack.us/img853/4350/unavngivetpn.png The Attempt at a Solution \int_{-L/2}^{L/2} [R^2 + (Z-Z_0)^2]^{1/2} -...

Homework Statement http://img842.imageshack.us/img842/2816/unavngivettz.png My problem is that I'm confused about a hint I was given in this problem. I usually use the law of cosine to find the length of \vec{r}-\vec{r'} in sphere problems. But the hint I have says that I should make it...

Oh there seems to be one more thing I don't quite get. This whole problem was how to calculate the potential of a hollow sphere With the equation like this: \phi = \frac{Q}{8 \pi \epsilon_0} \frac{|R + Z| - |R - Z|}{R Z} It seems that you are able to remove the absolute values when specified...

Your last comment did the job. Thank you ^^