[johnconnor92]

I'm very sorry for not putting the spoiler tags coz it's too difficult doing it with my phone.

Anyways is my explanation for the first part correct? As for the second part, is my drawing acceptable? I Googled but I couldn't get a proper diagram to illustrate. Also I'm stuck at the final part. Is my working correct? The guide says

In the second part, start from an eq P = V2/R for the power dissipation and note that the total resistance is (rho1 + rho 2)h/A. This part should then be fairly straightforward.

[Coursework.info]

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[Stonebridge]

Part a)
Much simpler than you imagine.
Just show that current density is independent of A, the cross section.

R=ρL/A

I = V/R
current density
I/A = V/(RA)

Sub for R in the second equation and A will cancel.

b)
Start with P = E²/R

Sub for R=ρL/A

You are told E is prop to temperature difference and the temperature difference is uniform.
This means that the emf is proportional to the length!

So finally sub E = kL

That's all you need to do.