Three equal resistors connected in series across a source of $e.m.f.$ together dissipate $10\, watt$. If the same resistors are connected in parallel across the same $e.m.f.$, then the power dissipated will be .............. $watt$
A$10$
B$30$
C$10/3$
D$90$
AIPMT 1998, Medium
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D$90$
d (d) In series ${P_S} = \frac{P}{n}$ $ \Rightarrow $ $10 = \frac{P}{3}$
$ \Rightarrow $ $P = 30\,W$
In parallel ${P_P} = nP = 3 × 30 = 90\, W$
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