Refer to the circuit diagram given below. The heat generated across the 6Ω resistance in 100 second is 100αJ. The value of α is ____. (Nearest integer)
Answer: 3477
Solution
Let the junction where the 3Ω, 6Ω and 4Ω branches meet be at potential x, with the lower rail as reference. The branch currents leaving the junction sum to zero: 6x−3+3x−2+4x=0, the 3 V and 2 V sources setting the far ends of the 6Ω and 3Ω branches. Clearing denominators, 2(x−3)+4(x−2)+3x=0⇒9x=14, so x=914 V. The current in the 6Ω branch is i=63−x=63−14/9=5413 A. The heat in 100 s is H=i2Rt=(5413)2×6×100=34.77 J =100α. Hence α=3477.