In the circuit shown, the resistance $r$ is a variable resistance. If for $r = fR,$  the heat generation in $r$ is maximum then the value of $f$ is 

821-992

  • [JEE MAIN 2016]
  • A

    $\frac {1}{4}$

  • B

    $1$

  • C

    $\frac {1}{2}$

  • D

    $\frac {3}{4}$

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