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**CIRCUIT ANALYSIS AND TECHNIQUES**

Kirchoff's Voltage Law

The '+' signs define the reference
direction for positive voltage or potential difference. The quantity **Us**
specifies the magnitude of the source voltage and its algebraic sign
with respect to the reference. If **Us** has a value of
+12V, the voltage of node **b** with respect to node **a** is positive.

By Kirchoff's voltage law, the
algebraic sum **Σ****u**
of the voltages around a loop at any instant is zero.

Σu = 0 = Uba
+ Ucb + Udc + Uad

Uba means '*the voltage of ***b** with respect to
**a**'.