A student writes for a junction, 'the algebraic sum of currents at a node is zero.' This is equivalent to Kirchhoff's Current Law provided
AAll currents are treated as positive regardless of direction
BCurrents entering and leaving are assigned opposite signs
COnly incoming currents are included
DThe node has exactly three branches
Answer & Solution
Correct answer: B. Currents entering and leaving are assigned opposite signs
The statement 'algebraic sum is zero' works only when a sign convention is used, such as currents entering positive and leaving negative, or vice versa. Then KCL becomes $\sum I=0$, equivalent to incoming current equals outgoing current.
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