Figure shows a part of an electric circuit. The potentials at points a, b and c are 30 V, 12 V and 2 V respectively. The current through the 20 resistor will be

Question

G1 Physics · Accepted Answer

Use the node potentials marked in the circuit and apply Kirchhoff's current law at the junction connected to the 20 Ω resistor. The current through each adjacent branch is obtained from I = (V₁ - V₂)/R Substituting the given node potentials 30 V, 12 V and 2 V in the branch equations and applying KCL gives the current through the 20 Ω resistor as I = 0.4 A Hence option C follows.