Recent content by sweep123

1. Charge distribution in a conductor (using maxwell's equations)

aha. I get it, Thanks alot thats brilliant. Don't think I would have ever got that on my own:smile:

3. Charge distribution in a conductor (using maxwell's equations)

Okay so Jfree=J. also D=εE so E=D/ε and therefore J=σD/ε edit: so ∇ · σD/ε = −∂(ρfree)/∂t or (∇σ/ε)· D + (σ/ε)(ρfree) = −∂(ρfree)/∂t Doesn't feel like im getting anyhere
4. Charge distribution in a conductor (using maxwell's equations)

I could sub the first eq into the second to get the divergence of current density equals the negative differential of the divergence of the electric displacement field, or ∇ · Jfree = −∂(∇ · D)/∂t Can Jfree and total J be considered to be the same thing in this example? Also I will lose ρ...
5. Charge distribution in a conductor (using maxwell's equations)

Homework Statement Show that any charge distribution in a conductor of conductivity σ and relative permittivity κ vanishes in time as ρ = ρ0exp(−t/ζ) where ζ = κǫ0 σ Homework Equations Maxwell's equation ∇ · D = ρfree equation of continuity for a free charge density ∇ · Jfree =...
6. Solving second order unhomogonous equations

oh yeah. i should have spent a bit more time on that. Thanks
7. Solving second order unhomogonous equations

ive just tried substituting the particular integral y(x)= c1(x^2)sin(x)+c2(x^2)cos(x)+xc3sin(x)+xc4cos(x) into y"+y=xsinx. I end up with 2c1sin(x)+4xc1cos(x)+2c2cos(x)-4xc2sin(x)+2c3cos(x)-2c4sin(x)=xsin(x) This doesn't look solvable. Ive checked my differentiating a couple of times and...
8. Solving second order unhomogonous equations

thanks. thats really helpful. is there anyway of knowing what the particular integral is for any unhomogenous second order differential equation, or is it just trial and error?
9. Solving second order unhomogonous equations

Homework Statement solve y"+y=xsin(x) , initial conditions y(0)=0, y'(0)=1 Homework Equations The Attempt at a Solution I know that when right hand side equals something like sin(x), then the particular integral is xc1sin(x)+xc2cos(x). I am unsure what the particular integral...
10. Why hasnt anyone viewed my question.

I understand that people are only helping voluntarily. It is just a bit frustrating watching new topics popping up at the top which get replies very quickly and then watching my topic move further and further down the page.
11. Why hasnt anyone viewed my question.

I did all the things on the FAQ and yet still noone has viewed my question about the wave equation. Why is this?
12. Satisfying wave equation

[SOLVED] Satisfying wave equation Homework Statement Confirm that the following wave satisfies the wave equation and obtain an expression for the velocity of a wave Y=Asin(2x-5t)*e^(-2t) Homework Equations the wave equation is (d^2y/dt^2)=(V^2)*(d^2y/dx^2) The Attempt at a...
13. Photometry- zero points of telescopes.

Homework Statement I need to calculate the zero point of the telescope and camera i used. Homework Equations The Attempt at a Solution I have count rates of various points on the screen in a 19x19 pixel box of a standard star using the two filters V and R. Ive used exposure...
14. Interplanar spacing 'd'

Does anyone know the interplanar spacing of the crystals NaCl and KCl. Thanks
15. Mechanics: mass on moving slope. no friction

1. Homework Statement A wedge with mass M rests on a frictionless horizontal table top. A block with mass "m" is placed on the wedge. There is no friction between the block and the wedge. The system is released from rest. A. Calculate the acceleration of the wedge. B. Calculate the...