Question

The resistivity of a ferric-chromium-aluminium alloy is 51 X 10^-8 Ω-m. A sheet of the material is 15 em long. 6 em wide and 0.014 em thick. Determine resistance between (a) opposite ends and (b) opposite sides.

Answer 1

(a) As seen from Fig. (a) in this case

l = 15cm = 0.15cm

A = 6 x 0.014 = 0.084cm²

= 0.084 x 10^-4m²

R = ρ(l/A) = (51 x 10^-8 x 0.15)/(0.84 x 10^-4)

= 9.1 x 10^-3Ω

(b) As seen from fig. (b)

l = 0.014cm = 14 x 10^-5

A = 15 x 6 = 90cm² = 9 x 10^-3m²

R = 51 x 10^-8 x 14 x 10^-5/9 x 10^-3 = 79.3 x 10^-10Ω