Question 370 of 380

Four bulbs ${B}_{1}$, ${B}_{2}$, ${B}_{3}$ and ${B}_{4}$ of $100W$ each are connected to $220V$ main as shown in the figure. The reading in an ideal ammeter will be

A$0.90A$B$1.35A$C$0.45A$D$1.80A$

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Answer: (B) $1.35A$

The resistance of any bulb$={V}^{2}/P$

Current through ammeter at shown position$=3{i}_{1}$
current in any $1$ bulb$={i}_{1}=\dfrac{V}{R}=\dfrac{V}{{V}^{2}/P}$$=\dfrac{P}{V}=\dfrac{100}{220}$
Through ammeter, $\Rightarrow {i}_{net}=3{i}_{1}=\dfrac{300}{220}$$=1.35A$

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