. A voltage is applied between all opposite faces of the block and the corresponding currents were recorded. What is the maximum current measured in Amps if the minimum current recorded is ?
A rectangular conducting homogeneous (which means the material is the same throughout) block has dimensions
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We know that: R = A ρ l where R = Resistance , ρ = Specific Resistance , l = length , A = Area .
We can rewrite the equation by multiplying I so that both sides become: I R = A ρ l I From Ohm's law V = I R therefore: V = A ρ l I ⟶ I = ρ l V A For minimum current A is minimum and length is maximum: Hence A = 2 × 1 and l = 3 1 = 3 ρ 2 V ρ V = 2 3 For maximum current A is maximum and l is minumum: Hence A = 2 × 3 and l = 1 : I = ρ 6 V = 6 × 2 3 = 9 mA