Electrical Power & Heating Effect question from NEET 2011 (AIPMT, Prelims)

Answer: (c)

1. $P_9 = \dfrac{V^2}{9} = 36 \Rightarrow V = 18\text{ V}$ across the parallel pair.
2. $I_9 = 18/9 = 2\text{ A}$, $I_6 = 18/6 = 3\text{ A}$, total $I = 5\text{ A}$.
3. Voltage across $2\ \Omega$: $5 \times 2 = 10\text{ V}$.
4. So the answer is (c) 10 volt.