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Unformatted text preview: 23. We use J = E/ρ, where E is the magnitude of the (uniform) electric ﬁeld in the wire, J is the magnitude
of the current density, and ρ is the resistivity of the material. The electric ﬁeld is given by E = V /L,
where V is the potential diﬀerence along the wire and L is the length of the wire. Thus J = V /Lρ and
(10 m) 1.4 × 104 A/m = 8.2 × 10−4 Ω · m . ...
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