10.2.1—Kirchhoff’s first law and understand that it is a consequence of
- Syllabus
- 9702–2028–2029
- Objective
- 10.2.1
- Level
- AS
Kirchhoff’s first law expresses charge conservation at a junction
At a circuit junction, total current entering equals total current leaving: ΣI_in=ΣI_out.
Choose current directions before solving; a negative answer means the true direction is opposite to the assumed arrow.
If 2.0 A and 0.5 A enter a node and one branch carries 1.5 A out, the remaining branch carries 1.0 A out.
Current is not “used up” at a junction; charge conservation determines the branch relation.
ConceptA-Level CAIE Physics AS