In a potentiometer experiment two cells of $e.m.f.$ $E_1$ and $E_2$ are used in series and in conjunction and the balancing length is found to be $58\, cm$ of the wire. If the polarity of $E_2$ is reversed, then the balancing length becomes $29\, cm$. The ratio $\frac{{{E_1}}}{{{E_2}}}$ of the $e.m.f.$ of the two cells is
  • A$1:1$
  • B$2:1$
  • C$3:1$
  • D$4:1$
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