Q: A rectangular block has dimensions 5 cm × 5 cm × 10 cm. Calculate the resistance measured between (a) two square ends (b) the opposite rectangular ends. Specific resistance of the material is 3.5 × 10-5 Ω m.
Sol. (a) Resistance between two square ends $\large R_1 = \rho \frac{l}{A}$
$\large R_1 = 3.5 \times 10^{-5} \times \frac{10 \times 10^{-2}}{5 \times 5 \times 10^{-4}}$
= 1.4 × 10-3 Ω
(b) Resistance between the opposite rectangular ends $\large R_2 = \rho \frac{l}{A}$
$\large R_2 = 3.5 \times 10^{-5} \times \frac{5 \times 10^{-2}}{5 \times 10 \times 10^{-4}}$
= 1.4 × 10-4 Ω