Electrical Power & Heating Effect question from NEET 2006 (AIPMT)

Answer: (a)

1. $P_8 = i_2^2 \times 8 = 2 \Rightarrow i_2 = 0.5\text{ A}$, so the branch voltage is $0.5 \times 8 = 4\text{ V}$.
2. Upper branch $(1 + 3) = 4\ \Omega$: $i_1 = 4/4 = 1\text{ A}$.
3. $P_3 = i_1^2 \times 3 = 3\text{ W}$.
4. So the answer is (a) 3.0.