Electric Circuits 8th Edition 61

# Electric Circuits 8th Edition 61 - To use Kirchhoff's...

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To use Kirchhoff's curent law, an algebraic sign co[esponding to a reference direction must be assigned to every current at the node. Assigning a positive sign to a current leaving a node requires assigning a negative sign to a cu[ent entering a node. Convenely, giving a negative sign to a current leaving a node requires giving a positive sign to a current entering a node. Applying Kirchhoff's curent law to the four nodes in the circuit shown in Fig. 2.15, using the convention that currents leaving a node are considered positive, yields four equations: j"-i1 :0, -ic-r:t), q \=t)' (2.16) (?.17) (2.18) (2.1e) Note that Eqs. 2.1G2.19 are not an independent set, because any one of the four can be dedved hom the ottrer tbree. In any cilcuit witl r nodes. l' 1 independent crment equations cail be dedved from Kirchhoffs current law.r Let's disiegard Eq. 2.19 so that we have six independent equations, namely, Eqs.2.13-2.18. We need one more, which we can de ve from K cbloff's voltage law.
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