Two identical square rods of metal are welded end to end as shown in figure $(i)$ , $20$ calories of heat flows through it in $4$ minutes. If the rods are welded as shown in figure $(ii)$, the same amount of heat will flow through the rods in ....... $\min.$

80-4

  • A

    $1$

  • B

    $2$

  • C

    $4$

  • D

    $16$

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