Posted by **Physics** on Thursday, May 13, 2010 at 1:22am.

The inner conductor of a coaxial cable has a radius of 0.900 mm, and the outer conductor's inside radius is 5.00 mm. The space between the conductors is filled with polyethylene, which has a dielectric constant of 2.30 and a dielectric strength of 18E6 V/m. What is the maximum potential difference that this cable can withstand?

no idea what to do...

thought it was

V= 18E6*d/k

but it was wrong...

- Physics -
**Damon**, Thursday, May 13, 2010 at 5:02am
18*10^6 V/m = 18*10^3 Volts. millimeter

Voltage = integral E dr from inner to outer r

2 pi E r = c constant (Gauss, therefore E is maximum beside the inner radius)

so

E = c/(2 pi r)

V = integral (c/2pi) dr/r

V = (c/2pi) ln(Router/Rinner)

V = (c/2pi) ln (5/.9) = 1.71 c/2 pi

now Emax is at r = .9

Emax = c/(.9*2pi)

c = .9*2pi (18*10^6)

so

V = 1.71 * .9 * 18 * 10^3

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