\(C\,\, = \,\,\frac{{2\pi {\varepsilon _0}\ell }}{{{{\log }_e}\,\left( {\frac{b}{a}} \right)}}\,\, \Rightarrow \,\,Length\,\,\,L\,\, = \,\,\frac{C}{{2\pi { \in _0}}}\,\,{\log _e}\,\,\left( {\frac{b}{a}} \right)\)

અહિં \(C-\) અચળ છે. 

\(\therefore \,\,L\,\, = \,\,{\log _e}\,\,\left( {\frac{b}{a}} \right)\)

\(\frac{{{L_1}}}{{{L_2}}}\,\, = \,\,\frac{{{{\log }_e}\,\,\left( {\frac{{{b_1}}}{{{a_1}}}} \right)}}{{{{\log }_e}\,\,\left( {\frac{{{b_2}}}{{{a_2}}}} \right)}}\,\, = \,\,\frac{{{{\log }_e}\left( {10} \right)}}{{{{\log }_e}\,\,\left( {20} \right)}}\)

અહી \(\frac{{{{\text{b}}_{\text{1}}}}}{{{{\text{a}}_{\text{1}}}}}\,\, = \,\,\frac{{10}}{1},\,\,\frac{{{b_2}}}{{{a_2}}}\,\, = \,\,\frac{{20}}{1}\)

\(\therefore \,\,\frac{{{L_2}}}{{L1}}\,\, = \,\,1.3\)