In a parallel circuit with several branches, how is the total current drawn from the power source related to the branch currents?

In a parallel circuit with several branches, how is the total current drawn from the power source related to the branch currents?

• A. Itotal equals the product of the branch currents
• B. Itotal equals the largest branch current
• C. Itotal equals the sum of the branch currents
• D. Itotal equals the current in the smallest resistance branch

Answer: (B)

In parallel circuits, the current that leaves the power source is shared among the branches, and the currents in those branches add up. The same voltage is across every branch, and at the junctions current must be conserved, so the total current supplied equals the sum of the currents in each branch: Itotal = I1 + I2 + I3 + …. This is why you can’t equate the total with a product, the largest branch current, or the smallest branch current. For example, if two branches draw 2 A and 3 A, the total drawn from the source is 5 A. Each branch current depends on its own resistance, since I = V/R for each branch, but the source current is always the sum of those branch currents.

In parallel circuits, the current that leaves the power source is shared among the branches, and the currents in those branches add up. The same voltage is across every branch, and at the junctions current must be conserved, so the total current supplied equals the sum of the currents in each branch: Itotal = I1 + I2 + I3 + ….

This is why you can’t equate the total with a product, the largest branch current, or the smallest branch current. For example, if two branches draw 2 A and 3 A, the total drawn from the source is 5 A. Each branch current depends on its own resistance, since I = V/R for each branch, but the source current is always the sum of those branch currents.