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Current Electricity question

2019 · Q142
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Current Electricity question

2019 · Q142

NEETPhysicsCurrent ElectricityMCQ+4 / −1
Six similar bulbs are connected as shown in the figure with a DC source of emf E, and zero internal resistance.

The ratio of power consumption by the bulbs when (i) all are glowing and (ii) in the situation when two from section A and one from section B are glowing, will be : NEET 2019 Physics - Current Electricity Question 41 English
  1. A
    4 : 9
  2. B
    9 : 4
  3. C
    1 : 2
  4. D
    2 : 1
View written solutionFree

Correct answer: B

(i) When all bulbs are glowing, from the given figure.

NEET 2019 Physics - Current Electricity Question 41 English Explanation 1

Equivalent resistance, Req = R3+R3=2R3{R \over 3} + {R \over 3} = {{2R} \over 3}3R​+3R​=32R​

Initial Power, (Pi) = 3E22R{{3{E^2}} \over {2R}}2R3E2​ ......(1)

(ii) When two section A and one from section B are glowing.
NEET 2019 Physics - Current Electricity Question 41 English Explanation 2


Req = R2+R{R \over 2} + R2R​+R = 3R2{{3R} \over 2}23R​

Final Power, (Pf) = 2E23R{{2{E^2}} \over {3R}}3R2E2​

∴\therefore∴ PiPf=3E22R×3R2E2{{{P_i}} \over {{P_f}}} = {{3{E^2}} \over {2R}} \times {{3R} \over {2{E^2}}}Pf​Pi​​=2R3E2​×2E23R​ = 9 : 4

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