I have gotten this far:
Using cos(2θ) = 1-tan2θ / 1+tan2θ From a previous question:
Let θ= arctan(x):
cos(2θ) = 1-tan2(arctan(x)) / 1+tan2(arctan(x))
=1-x2 / 1+x2
Where x2 cannot equal 0 or a negative number
Have I done this in the right way and if so is this as far as I can...
Use Gauss' law as though the cylinder is not there?
In which case to calculate using E= λ/(2πε_0 r) and use the 2.5mm as the radial distance?
Is there any different concepts behind this scenario compared to using a gaussian surface?
I'm a little stuck on the theory behind this question:
(in relation to a line of infinite charge: a wire)
A hollow cylindrical metal tube with inner radius 2.5mm is now placed around the wire, to form a coaxil cable. What will be the charge per unit length on the inner surface of the tube...