Network Theorem Kirchoff's Law Tutorials

Kirchoff's Law Facts and tutorials

Kirchoff's Current Law (KCL) 
In any electrical network. The algebraic sum of the currents meeting at a point or junction is zero. Here it is assumed that incoming current to be positive and outgoing current to be negative.

Kirchoff's Voltage Law (KVL)
The algebraic sum of the products of currents and resistance in each of the conductors in any closed path or mesh in a network plus the algebraic sum of the electromotive force in the path is zero.

Sign Conventions for Kirchoff's Law

• A rise in voltage shall be given a plus sign and fall in voltage drop shall be given a negative voltage sign.
• In a resistance if we traverse in the direction of current. It is a voltage drop. This is because the current flows from higher potential to lower potential. This is voltage drop. It is given to be a negative voltage sign.
• In a resistance if we go in the direction, opposite to direction of flow of current, we are going from lower potential to higher potential. Going from lower to higher potential means voltage rise and shall be given a positive voltage sign.
• In a battery if we go from negative voltage sign terminal of battery to positive voltage sign this is voltage rise. This shall be given a positive voltage sign.
• In a battery if we go from positive voltage sign terminal of a battery to negative voltage sign terminal, this is voltage drop. It should be given a negative voltage sign.

Method to solve circuits by kirchoff's Law

• Draw a large clear diagram of the network to be solved showing the values of all resistors and the polarity and values of all sources of electromotive force letter the nodes and number of meshes.
• Arbitrarily choose direction for the currents in each branches. There is no point in wasting time for trying to indicate the true current directions since, in the majority of the cases, it is quite impossible to tell.
• Place plus and minus signs on each resistors to indicate the direction of the potential difference across it. These potential differences must be constant with the directions of the assumed branch currents.
• Write an equation for each in the network, using Kirchoff's second law, traversing the meshes in the clock wise direction.
• Solve the resulting simultaneous equations.

Take note that, it should be noted that Kirchoff's law are applicable both direct current and alternating current. Voltage and current, However in the case of alternating current and voltages any electromotive force or self-inductance that existing across a capacitor should also be taken into account.

Free pdf file for network Theorem
The fundamental laws that govern electric circuits are the Ohm’s Law and the Kirchoff’s
Laws.