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 2019]

A)  1 : 2    

B)       2 : 1

C)  4 : 9                

D)       9 : 4

Correct Answer: D

Solution :

[d] 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)

\[\frac{{{P}_{1}}}{{{P}_{2}}}=\frac{3}{2}\times \frac{3}{2}=\frac{9}{4}\]