The circuit given below is for the operation of an industrial fan. The resistance of the fan is $3$ $o h m s$ . The regulator provided with the fan is a fixed resistor and a variable resistor in parallel.
Under what value of the variable resistance given below, Power transferred to the fans will be maximum? The power source of the fan is a dc source with internal resistance of $6$ $o h m$ .

3 Ω

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0

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6 Ω

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Solution

The correct option is B $0$
As we know that if resistor are connected in parallel then current will be divided in it,hence power consumption will be more.
Power(P) $= I^{2} R$
P $\propto$ $I^{2}$
here power will vary square times the current across it so to obtained maximum power in the above circuit we keep the position of variable resistor at null point,hence it will behave like a simple wire( $R_{v a r i a b l e} = 0$ ) and current will be same throughout the network.

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