In a parallel circuit, how does the total current relate to the currents in each branch?

• A. It equals the largest branch current
• B. It equals the sum of the branch currents
• C. It equals the product of the branch currents
• D. It equals the average of the branch currents

Answer: (B)

In a parallel circuit, currents split at the junctions and then recombine back to the source. The total current provided by the source is the sum of the currents in each branch, by conservation of charge. So the current from the source equals I1 plus I2 plus In for all branches. For example, if two branches draw 2 A and 3 A, the total current from the source is 5 A. This is not determined by the largest branch current, nor by a product or an average of the branch currents. The branch currents depend on the branch resistances and the same parallel voltage, with each I = V/R_branch; summing those branch currents gives the total.