Six similar bulbs are connected as shown with a DC source of emf E and zero internal resistance. The ratio of power consumption when (i) all bulbs are glowing and (ii) two from section A and one from section B are glowing is: [Diagram: Image]
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Question

Six similar bulbs are connected as shown with a DC source of emf E and zero internal resistance. The ratio of power consumption when (i) all bulbs are glowing and (ii) two from section A and one from section B are glowing is: [Diagram: Image]

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G1 Physics · Accepted Answer

Step 1: Original circuit has two sets of three parallel bulbs (R/3 each) connected in series. Initially R(eq) = 2R/3 and P₁ = E²/(2R/3) = 3E²/(2R). Step 2: Two bulbs glowing in section A give R/2; one in section B gives R. These are in series: R′ = 3R/2. Step 3: P₂ = E²/(3R/2) = 2E²/(3R). Step 4: P₁/P₂ = (3/2)/(2/3) = 9/4.