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gruba
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Homework Statement
Coaxial cable has double layered dielectric.
a=2mm, b=4mm, c=8mm, εr1=3, εr2=4.5, Uab=1000V
1. Calculate capacitance per unit length of a cable.
2. Calculate inner and outer charge densities of a cable.
2. Homework Equations
Gauss law
C'=Q'/U
σ = nD
σp = nP
3. The Attempt at a Solution
After applying Gauss law for dielectrics, I get electric field:
E=Q'/(2πε0(εr1+εr2r)).
Limits of integration for voltage: (a - b) + (b - c)
U=(Q'(ln(b/a)+ln(c/b)))/(2πε0(εr1+εr2))
Then, C'=(2πε0(εr1+εr2))/(ln(b/a)+ln(c/b))
This gives me C'=288pF/m but in my books solution it is C'=144pF/m.
Could someone check this.
Thanks for replies.