Recent content by chocolatecake

And ω is the angular frequency in rad/s

Well N is the number of turns, Φ is the magnetic flux, B is the magnetic field and A the area.

Is the amplitude is the maximum displacement in the y direction? So I have to find the derivative? That I do understand, but I found many different equations for Φ and I don't know which one is the correct one. For example, here it says that ##Φ=NBAcosθ## , on this website ##Φ=NBA## and...

Another problem is, is that t is not given, so I can't really solve the equation.

Ok, but why do I have to use this equation?

Homework Statement [/B] A radio transmitter radiates isotropically at the frequency of 90.8 MHz. The peak magnetic field at a receiver, 9km from the transmitter, is ##9x10^{-10}T##. Calculate the maximum amplitude of the induced emf in a 12 turn coil with area A = ##90cm^{2}## at the receiver...

But that's a different equation from the one in the problem, isn't it?

And thank you to the others who helped as well of course! :smile:

Great, I will try that! Thank you for your help and your time! :smile:

Now I got it! :partytime: ##-2R(R^2+Rr+Rr+r^2)+R^3+3R^2r+3Rr^2+r^3=0## ##-2R^3-2R^2r+(-2R^2r)-2Rr^2+R^3+3R^2r+3Rr^2+r^3=0## ##-R^3-R^2r+Rr^2+r^3=0## and then if I substitute R=r, I get the same as you did: ##-R^3-R^3+R^3+R^3=0## Thank you! But now I still have to find the absolute maximum, or...

Well, the numerator was ##-2RV^2##, so I rewrote it as ##-2R(-2)V^2##. But I just realized that this was nonsense because it would only work if the numerator was ##-2(R+V^2)##. I'll try it again, give me a few minutes.

But if I substitute R+r with S, then I have three variables. And I don't understand where the ##\frac{P}{V^2}## is coming from. If we have a P there, then there are four variables (S, V, P and R).

Ok, that makes sense to me now. If I do it, it looks like this: ##\frac{-2R(-2)V^2}{(R+r)^3}+\frac{V^2}{(R+r)^2}=0## divide by ##V^2## : ##\frac{4R}{(R+r)^3}+\frac{1}{(R+r)^2}=0## common denominator: ##\frac{4R(R+r)^2}{(R+r)^5}+\frac{(R+r)^3}{(R+r)^5}=0## multiply by common denominator...

I understand now how to find the derivative but I don't understand how to simplify to ##-R^3-R^2r+Rr^2+r^3 =0## How did you get R^2r or Rr^2? I tried using the binomial theorem for (R+r)^2 and (R+r)^3 but that made everything even more confusing. What I ended up with is basically this...

Thank you so much for your help! I thought that the derivative might be wrong. Thanks for the idea to convert the equation into a product. It's so much easier, I'm always going to do that from now on. Anyways, I tried it on my own, but I got something different than you have. I'm not sure if my...