Three light bulbs of 40, W,60, W,and 100, W a | vedclass

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Question

(A) The power consumed by a bulb is given by $P = I^2 R$. In a series circuit,the current $I$ flowing through all bulbs is the same. The resistance $R

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$40\, W$

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(A) The power consumed by a bulb is given by $P = I^2 R$. In a series circuit,the current $I$ flowing through all bulbs is the same. The resistance $R$ of a bulb is related to its rated power $P_{rated}$ and rated voltage $V$ by $R = V^2 / P_{rated}$. Since $V$ is constant for all bulbs,$R \propto 1 / P_{rated}$. Therefore,the power consumed is $P_{consumed} = I^2 	imes (V^2 / P_{rated}) \propto 1 / P_{rated}$. Since the $40\, W$ bulb has the lowest rated power,it has the highest resistance. Consequently,the $40\, W$ bulb consumes the most power and will glow the brightest.

Three light bulbs of $40\, W$,$60\, W$,and $100\, W$ are connected in series with a $220\, V$ source. Which one of the bulbs will glow brightest?

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