Heater of electric kettle is made of a wire of length $L$ and diameter $d$. It takes $4$ minutes to raise the temperature of $0.5 \ kg$ water by $40\ K$. This heater is replaced by a new heater having two wires of the same material, each of length $L$ and diameter $2 d$. The way these wires are connected is given in the options. How much time in minutes will it take to raise the temperature of the same amount of water by $40K$ ?

$(A)$ $4$ if wires are in parallel

$(B)$ $2$ if wires are in series

$(C)$ $1$ if wires are in series

$(D)$ $0.5$ if wires are in parallel.

  • A$(B,D)$
  • B$(B,C)$
  • C$(A,C)$
  • D$(A,D)$
IIT 2014, Advanced
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