Title: 1.5 LTC reward for equations needed and help with first year physics work Post by: newuser20 on April 02, 2014, 02:05:27 PM http://imgur.com/ZyiokLn
This is the problem, I need the equations to calculate the problems, and then some feedback on if its right. 2 LTC reward if this is done tonight Title: Re: 1.5 LTC reward for equations needed and help with first year physics work Post by: newuser20 on April 02, 2014, 02:07:58 PM Bonus for clarity
Title: Re: 1.5 LTC reward for equations needed and help with first year physics work Post by: Sgt.Hartman on April 02, 2014, 06:04:36 PM Ok let me try the first one:
a) Hx = Ey/ZF0 (only got x-component of magnetic field) b) P = |E|2/2*ZF0 c) Sz = Ey x Hx = -Ey*Hx (Poynting points into z-direction) Am I right? (has been toooo long) :D Title: Re: 1.5 LTC reward for equations needed and help with first year physics work Post by: newuser20 on April 02, 2014, 07:39:12 PM For the first I used V x E = -dB/dt
to get: KE_o sin (wt-kx+psi) = -DB/dt B = kE_o/w * cos(wt-kx+psi) * i hat I'm not sure this is right or what the Zfo was in your solution. b) 1/2 epsilon_o E^2 C) k*(E_o)^2/W cos^2(wt-kx+psi) * 1/u_o can you check what you wrote was the same ? Title: Re: 1.5 LTC reward for equations needed and help with first year physics work Post by: Sgt.Hartman on April 02, 2014, 09:08:29 PM I didnt quite get what you elaborated...
a) I meant ZF0 is free space impedance 377 ohms. If you have the E-field given, then also H-field ist given via ZF0 b) U use a formular for static fields. But as far as I see we have a constant frequency continuous wave travelling in free space. Since its sin-wave we have to get average rms value that is expressed with 1/2 c) Definition of poynting vector is: S = E x H whereas all components are 3d vectors. Title: Re: 1.5 LTC reward for equations needed and help with first year physics work Post by: newuser20 on April 02, 2014, 09:37:29 PM let me start with saying I've missed a few lectures so im learning this online.
http://en.wikipedia.org/wiki/Magnetic_field First part under 'Maxwell's equations' section V being the triangle thing, which i take to mean d/dx+d/dy+d/dz Which gives you a result in the i direction, nothing in j,k (y,z). Honestly ive never seen Z before, do you mind showing me the equations you used ? C) This is just the cross product of the perpendicular electric and magnetic fields and is correct ? Title: Re: 1.5 LTC reward for equations needed and help with first year physics work Post by: newuser20 on April 02, 2014, 09:42:28 PM next part:
Ok so for the next part the parity of the box confuses me the equation of motion is psi(x) = Ceax + De-ax Ce-aL = Bsin(-kL) DeaL = Bsin(kL) For odd function C = -D even solution is similar with C = D But what does this mean ? To find the energy You use the eq E psi(x) = -h/2m d2psi(x)/dx2 + V(x) Psi(x) Diff twice and plug in etc ? c) will post later Title: Re: 1.5 LTC reward for equations needed and help with first year physics work Post by: Sgt.Hartman on April 03, 2014, 08:16:01 AM let me start with saying I've missed a few lectures so im learning this online. http://en.wikipedia.org/wiki/Magnetic_field First part under 'Maxwell's equations' section V being the triangle thing, which i take to mean d/dx+d/dy+d/dz Which gives you a result in the i direction, nothing in j,k (y,z). Honestly ive never seen Z before, do you mind showing me the equations you used ? C) This is just the cross product of the perpendicular electric and magnetic fields and is correct ? http://en.wikipedia.org/wiki/Impedance_of_free_space (http://en.wikipedia.org/wiki/Impedance_of_free_space) Section plane wave solution. We have time continuous fields. That simplify maxwells equations a lot. ad c) Yes but consider peak value and rms value. It depends what you have, then you have to add 1/2 or not. Do you have a solution somewhere??? Second part let me take a look into my cryst... eeeeh books ;D |