d
તાંબાના  તાર માટે \({\rho _{\text{A}}}{\text{  =   }}{\rho _{\text{B}}}{\text{ }}\)

\({\text{A}}\) તાર માટે \({R_A}\,\, = \,\,\frac{{{\rho _A}{l}}}{A}\,\, = \,\,\frac{{3{\rho _A}}}{A}\,;\,\)

\(\,B\) તાર માટે \(\,{R_B}\,\, = \,\,\frac{{{\rho _B}{l}}}{A}\,\, = \,\,\frac{{5{\rho _B}}}{A}\,;\)

\(\therefore \,\,\frac{{{R_A}}}{{{R_B}}}\,\, = \,\,\frac{{\frac{{3\rho A}}{A}}}{{\frac{{5{\rho _B}}}{A}}}\,\, = \,\,\frac{3}{5}\)          \([\because \,\,{\rho _A}\,\, = \,\,{\rho _B}]\)

\(\therefore \,\,\frac{{{R_A}}}{{{R_B}}}\,\, < \,\,1\,\)         \(\therefore \,\,{R_A}\,\, < \,\,{R_B}\)