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