At a junction, the current splits: some charge takes one branch, the rest takes the other. What must the two branch currents add up to?
Here is a battery driving two lamps on parallel branches. An ammeter next to the battery reads 0.5 A.
Ammeters in the branches settle it. They read 0.3 A and 0.2 A.
Compare the three readings: 0.3 A + 0.2 A = 0.5 A. That is the rule, seen in numbers.
Which rule describes the current in a parallel circuit?
Follow the current around. The battery supplies 0.5 A. At the junction, the current splits: 0.3 A flows into the first branch, and 0.2 A flows into the second. At the far junction the branch currents rejoin, and 0.5 A flows back to the battery.
Notice the split is not equal. In this circuit one branch carries 0.3 A and the other 0.2 A. Only the total is fixed by the rule.
The branches of a parallel circuit carry 0.8 A and 0.6 A. What current does the battery supply?
Write down the rule:
The branch currents add up to the supply current.
Add the branch currents:
0.8 A + 0.6 A = 1.4 A
The battery supplies 1.4 A.
The branches of a parallel circuit carry 0.6 A and 0.9 A. What current does the battery supply, in A?
A third branch carrying 0.5 A is added, and the first two branches still carry 0.8 A and 0.6 A. What current does the battery supply now?
The rule covers every branch: the branch currents add up to the supply current.
Add all three branch currents:
0.8 A + 0.6 A + 0.5 A = 1.9 A
The battery supplies 1.9 A.
The battery of a two-branch parallel circuit supplies 2.0 A. Which pair of branch currents is possible?
Compare the two circuit types. In a series circuit, the current is the same at every point. In a parallel circuit, the branch currents add up to the supply current.
Parallel branches carry 0.7 A and 0.5 A. What current does the battery supply, in A?
A battery supplies 1.8 A to two identical lamps in parallel. What current flows through each lamp, in A?
In a two-branch parallel circuit, which part of the circuit carries the largest current?