Question
The four wires from a larger circuit intersect at junction $$A$$ as shown. What is the magnitude and direction of the current between points $$A$$ and $$B$$ ?
The four wires from a larger circuit intersect at junction $$A$$ as shown. What is the magnitude and direction of the current between points $$A$$ and $$B$$ ?
A.
$$2A$$ from $$A$$ to $$B$$
B.
$$2A$$ from $$B$$ to $$A$$
C.
$$3A$$ from $$A$$ to $$B$$
D.
$$3A$$ from $$B$$ to $$A$$
Answer :
$$3A$$ from $$A$$ to $$B$$
Solution :
Kirchhoff’s junction rule states that the algebraic sum of all currents into and out of any branch point is zero: $$\Sigma I = 0.$$ By convention, the sign of current entering a junction is positive and current leaving a junction is negative.
$$4A + 5A - 6A + {I_{AB}} = 0,$$ therefore $${I_{AB}} = - 3A.$$ The wire between points $$A$$ and $$B$$ carries a current of $$3A$$ away from the junction.
Kirchhoff’s junction rule states that the algebraic sum of all currents into and out of any branch point is zero: $$\Sigma I = 0.$$ By convention, the sign of current entering a junction is positive and current leaving a junction is negative.
$$4A + 5A - 6A + {I_{AB}} = 0,$$ therefore $${I_{AB}} = - 3A.$$ The wire between points $$A$$ and $$B$$ carries a current of $$3A$$ away from the junction.
