Two wires of the same dimensions but resistivities `rho_(1)` and `rho_(2)` are connected in series. The equivalent resistivity of the combination is

Options

A. `(rho_(1)+rho_(2))/(2)`
B. `rho_(1)+rho_(2)`
C. `2(rho_(1)+rho_(2))`
D. `sqrt(rho_(1)rho_(2))`

Answer

A

Explanation

The effective resistance of combined wire
`R=R_(1)+R_(2)`
`rho ((l+l)/(A))=(rho_(1)l)/(A)+(rho_(2)l)/(A) " "[because " total length " L=l+l]`
or `rho=(rho_(1)+rho_(2))/(2)`