2.2C: Long Charged Rod
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- 5837
The field at a distance \(r\) from a long charged rod carrying a charge \(λ\) coulombs per meter is \(\frac{\lambda}{2\pi\epsilon_0 r}\). Therefore the potential difference between two points at distances \(a \text{ and }b\) from the rod \((a < b)\) is
\[\begin{align}V_b-V_a&=-\frac{\lambda}{2\pi\epsilon_0}\int_a^b \frac{dr}{r}. \\ \therefore V_a-V_b&=\frac{\lambda}{2\pi\epsilon_0}\ln (b/a).\tag{2.2.6} \\ \end{align}\]