Refer to the network shown in the figure. The three upper branches are identical, each containing three 5 V cells and three 3 Ω resistors in series, while the lower branch contains three 3 Ω resistors in series. What current flows between terminals A and B?
Options

Question

Refer to the network shown in the figure. The three upper branches are identical, each containing three 5 V cells and three 3 Ω resistors in series, while the lower branch contains three 3 Ω resistors in series. What current flows between terminals A and B?

Options

G1 Physics · Accepted Answer

Each of the three source branches has emf = 15 V and internal series resistance = 9 Ω. Three identical 15 V, 9 Ω branches connected in parallel have equivalent emf E(eq) = 15 V and equivalent resistance r(eq) = 9 ÷ 3 = 3 Ω. The lower branch between A and B has resistance R = 3+3+3 = 9 Ω. Thus the total circuit resistance is R(total) = 3+9 = 12 Ω. Therefore, I = 15 ÷ 12 = 1.25 A. Correct option: B.