Question

Two wires of equal diameters of resistivities `rho_(1)` and `rho_(2)` and length `x_(1)` and `x_(2)` respectively are joined in series. Find the equivalent resistivity of the combination.
A. `(rho_1 l_1 + rho_2 l_2)/(l_1 + l_2)`
B. `(rho_1 l_2 + rho_2 l_1)/(l_1 - l_2)`
C. `(rho_1 l_2 + rho_2 l_1)/(l_1 + l_2)`
D. `(rho_1 l_1 - rho_2 l_2)/(l_1 - l_2)`

Answer 1

Correct Answer - A
`R_(eq) = R_1 + R_2`
`(rho_(eq)(l_1 + l_2))/(A) = (rho_1 l_1)/(A) + (rho_2 l_2)/(A)`
`rho_(eq) = (rho_1 l_1 + rho_2 l_2)/(l_1 + l_2)`.