Electric Currents & Ohm's Law - Units of Resistivity example 7
Question : The resistivity of a ferric-chromium-aluminium alloy is 51 × 10−8 Ω-m. A sheet of the material is 15 cm long, 6 cm wide and 0.014 cm thick. Determine resistance between
(a) opposite ends and
(b) opposite sides.
Solution : (a) As seen from Fig. 1.5 (a) in this case,
l = 15 cm = 0.15 cm
A = 6 × 0.014 = 0.084 cm2
= 0.084 × 10−4 m2
= 9.1 × 10−3 Ω
(b) As seen from Fig. 1.5 (b) here
l = 0.014 cm = 14 × 10−5 m
A = 15 × 6 = 90 cm2 = 9 × 10−3 m2
∴ R = 51 × 10−8 × 14 × 10−5/9 × 10−3 = 79.3 × 10−10 Ω
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