| (i) If both the bulbs are connected in series then the total power consumption will be 60 W. |
| (ii) If only one bulb is connected then the total power consumption will be 30 W. |
| (iii) If the both bulbs are connected in parallel then the total power consumption will be 120 W. |
A) Only (i) and (ii)
B) Only (ii) and (iii)
C) Only (iii)
D) Only (i)
Correct Answer: C
Solution :
\[V=220V,\,P=60\,W\] \[P=\frac{{{V}^{2}}}{R}\] ?(i) As bulbs are connected in series, then \[P'=\frac{{{V}^{2}}}{{{R}_{eq}}}=\frac{{{V}^{2}}}{R+R}=\frac{{{V}^{2}}}{2R}\] or \[P'=\frac{1}{2}P\] (from (i)) or \[P'=\frac{60}{2}=30\,W\] As bulbs are connected in parallel, then \[\frac{1}{{{R}_{eq}}}=\frac{1}{R}+\frac{1}{R}\]or \[{{R}_{eq}}=\frac{R}{2}\] So power \[{{P}_{eq}}=\frac{{{V}^{2}}}{{{R}_{eq}}}=\frac{{{V}^{2}}}{R}\times 2\] or \[{{P}_{eq}}=2P=2\times 60=120\,W\]
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