
#1
Jan2110, 01:35 PM

P: 11

1. The problem statement, all variables and given/known data
This is a question on a past paper of a secondyear undergraduate physics paper. A parallel plate capacitor is charged and the voltage increases at a rate of dV/dt. The plate radius is R and the distance between the plates is d. (a) What is the electric field strength E(V,d) inside a parallel plate capacitor? (4 marks) (b) Find the electric flux for a circular area of radius r around the central axis (4 marks) (c) Derive the magnetic field strength B(r, R, d, dV/dt) (9 marks) 3. The attempt at a solution (a) Isn't this just E = V/d? Surely that's not worth 4 marks, but I can't imagine what else it could be. (b) Similarly, isn't this phi = 4 pi k q? (or q/epsilon 0 r^2) O_O Or is it phi = E*d, so E*pi*r^2? SURELY not?? (c) Got a bit stuck with this one. As I wasn't sure about phi, especially. Ended up with E = (μ0*I)/d + μ0*ε0*(q/ε0*r^2*dt) Not sure how to progress from there, and especially get it in terms of dV/dt. Any help would be great. 


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