In simple case, we can calculate the equivalent resistance as well as voltage and current in the circuit using Ohm’s law. But in more complex circuit or network the calculation is done with the help of Kirchhoff’s laws.
Kirchhoff’s Current Law:
“In any electrical network, the algebraic sum of the current meeting at a point is zero.”
In other words, whenever two or more than two conductors meet at a point, then the sum of current flowing towards the junction is equal to the sum of current flowing away from that point.
Sign rules for KCL:
All incoming currents to the junction may be taken as positive; while all outgoing currents taken as negative.
Kirchhoff’s Voltage Law:
“The algebraic sum of the product of current and resistance in each conductor in any closed loop or mesh in a network plus the algebraic sum of the voltages in that path is zero.”
Sign rules for KVL:
Give positive sign to all rise in voltage and negative sign to voltage drops.
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