c
\(\frac{{{R_1}}}{{{R_2}}}\,\, = \,\,\frac{{{{l}_1}}}{{100 - {{l}_1}}}\,\,\,\) માં

\({R_1}\, = \,\,\,10\,\Omega ,\,\,{R_2}\,\, = \,\,30\,\,\Omega \) મૂકતાં

\(\frac{{10}}{{30}}\,\, = \,\,\frac{{{{l}_1}}}{{100 - {{l}_1}}}\)

\(\therefore \,\,\,30{{l}_1}\,\, = \,\,1000\,\, - \,\,10{{l}_1}\)

\(\therefore \,\,\,{{l}_1}\,\, = \,\,25\,\,\) સેમી

હવ, અવરોધોની અદલા બદલી કરતાં \(R_1 = 30\, \Omega , R_2 = 10\, \Omega\)

\(\therefore \,\,\frac{{30}}{{10}}\,\, = \,\,\frac{{{{l}_2}}}{{100 - {{l}_2}}}\)

\(\,\therefore \,\,300\,\, - \,\,3{{l}_2}\,\, = \,\,{{l}_2}\,\,\,\)

\(\,\therefore \,{{l}_2} = \,\,75\) સેમી

તેથી તટસ્થ બિંદુ \(75 - 25 = 50\)  સેમી ખસશે.