Question

A current of 2 A flows in an electric circuit as shown in figure. The potential difference (VR – VS) , in volts (VR and VS are potentials at R and S respectively) is

Answer 1

-2

Answer 2

The circuit has three parallel branches between S and R with resistances 3Ω, (1Ω+2Ω)=3Ω, and (2Ω+1Ω)=3Ω. The total current of 2A divides equally among the three branches, so the current in each branch is 2/3 A. The potential difference across each branch from S to R is the product of the current in the branch and its total resistance. For the first branch, $V_S - V_R = (2/3 \text{ A}) \times 3 \Omega = 2$ V. The potential difference $(V_R - V_S)$ is the negative of $(V_S - V_R)$, which is $-2$ V.