Home › A student writes $I_1+I_2+I_3+I_4+I_5+I_6=0$ for…
A student writes $I_1+I_2+I_3+I_4+I_5+I_6=0$ for the junction in the figure without assigning any sign convention. Why is this incorrect? 
ABecause Kirchhoff's Current Law applies only to loops, not junctions
BBecause currents must be separated into entering and leaving groups, or assigned algebraic signs consistently
CBecause only two currents can meet at a junction
DBecause current is not conserved in branched circuits
Answer & Solution
Correct answer: B. Because currents must be separated into entering and leaving groups, or assigned algebraic signs consistently
KCL can be written as an algebraic sum equal to zero only if directions are represented by signs, such as taking entering currents positive and leaving currents negative. Without a sign convention, simply adding all magnitudes is not correct. For the shown figure, the proper grouped form is $I_1+I_2+I_3=I_4+I_5+I_6$.
