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## Homework Statement

Two long wires with the same cross section are arranged in air PARALLEL to each other . Assume both have opposite charge densities +λ and -λ. The distance between the axis of the wire is η times larger than the radius(r) of wires cross section . What would be the capacitance of the wires per unit lenth?

## Homework Equations

Electric field of any point between these wires at a distance x from the +λ charged wire is

λ/2πε[1/(x)+1/(ηr-x)]

## The Attempt at a Solution

The problem I am facing is about the limits to be used while integrating Electric field to get the potential .

We know that V=-∫Edx

(Between some limits)

So ∫Edx =λ/2πε[ln(x/ηr-x)]

And if I integrate it over 0 to ηr

The I will get stuff like ln 0 and ln∞ which are obviously not defined . Some other limits just dont get the right answer which is πε/ ln η . [/B]