question_answer

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 5-5-2019]

A) 1 : 2                 

B) 2 : 1

C) 4 : 9                             

D) 9 : 4

Correct Answer: D

Solution :

When all bulbs are glowing                         \[{{R}_{eq}}=\frac{R}{3}+\frac{R}{3}=\frac{2R}{3}\]             \[Power\,{{P}_{1}}=\frac{3{{E}^{2}}}{2R}\]----------------- (i)             In case two                         \[{{R}_{eq}}=\frac{3R}{2}\]             \[Power\,{{P}_{2}}=\frac{2{{E}^{2}}}{3R}\]--------------- (ii)             \[\frac{{{P}_{1}}}{{{P}_{2}}}=\frac{3}{2}\times \frac{3}{2}=\frac{9}{4}\]