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  4. A circuit consists of three identical lamps connected to a battery as shown in the figure. When the switch S is closed then the intensities of lamps A and B <img class=img-fluid question-image alt=Question src=https://cdn.tardigrade.in/q/nta/p-kdqotgyh7p8f.png />

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Q. A circuit consists of three identical lamps connected to a battery as shown in the figure. When the switch $S$ is closed then the intensities of lamps $A$ and $B$

Question

NTA AbhyasNTA Abhyas 2020Current Electricity

Solution:

After the closing of $ \, S, \, C$ bulb or lamp become short-circuited

Solution

the potential across $A$ and $B$ before the closing of $S=\frac{V}{3}$
Potential across $A$ and $B$ after the closing of $S=\frac{V}{2}$
As $P \propto V^{2}$
$\therefore \frac{P_{i}}{P_{f}}= \, \frac{4}{9}$
$P_{f}=\frac{P_{i} \times 9}{4}= \, 2.25 \, P_{i}$