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Q)

# How much power is dissipated as heat in the closed circuit ? What is the source of this power ?

$(A) 9 \times 10^{-3} W$
$(B) 90 \times 10^{-3} W$
$(C) 0.9 \times 10^{-3}W$
$(D) 900 \times 10^{-3} W$

\begin{align*} \text{Power dissipated in closed circuit due to flow of current } & = I^2R \\ & =(\frac{e}{R})^2 \times R = \frac{e^2}{R} \\ & = \frac{(9 \times 10^{-3})^2}{9 \times 10^{-3} } \\ & = 9 \times 10^{-3} W \end{align*}