Deriver $R = \frac{ρ l}{A}$ .

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Solution

If you consider $J = σ E$ or $ρ J = E$ as fundamental as well as V=IR, then we can derive the formula:

$E = \frac{V}{L}$ , since we're considering uniform cuboid

$J = \frac{I}{A}$ by definition

⟹ $\frac{ρ I}{A} = \frac{V}{L} ⟹ V = I \frac{ρ L}{A}$
Comparing with $V = I R$ we get $R = \frac{ρ L}{A}$

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Deriver R=ρlA.

If you consider J=σE or ρJ=E as fundamental as well as V=IR, then we can derive the formula:E=VL, since we're considering uniform cuboidJ=IA by definition⟹ρIA=VL⟹V=IρLAComparing with V=IR we get R=ρLA

Deriver $R = \frac{ρ l}{A}$ .