Data: R = 8 Ω, L = 8 m, E = 2 V, K = 1 µV/mm
= 1 × \(\frac{10^{-6} \mathrm{~V}}{10^{-3} \mathrm{~m}}\) = 10-3 \(\frac{\mathrm{V}}{\mathrm{m}}\)
K = \(\frac{V}{L}=\frac{E R}{\left(R+R_{\mathrm{B}}\right) L^{\prime}}\) where RB is the resistance in the box.
∴ 10-3 = \(\frac{2 \times 8}{\left(8+R_{B}\right) 8}\)
∴ 8 + RB = \(\frac{2}{10^{-3}}\)
= 2 × 103
∴ RB = 2000 – 8
= 1992 Ω