EC201 NETWORK THEORY NOTE
UNIT I BASIC CIRCUIT ANALYSIS 12 Ohm‟s law, Kirchoff‟s laws – DC and AC circuits – Resistors in series and parallel circuits – Mesh current and node voltage method of analysis for DC and AC circuits ( AC circuits at elementary level only) The terms which are used frequently in circuit analysis : Circuit - a circuit is a closed loop conducting path in which an electrical current flows. Path - a line of connecting elements or sources with no elements or sources included more than once. Node - a node is a junction, connection or terminal within a circuit were two or more circuit elements are connected or joined together giving a connection point between two or more branches. A node is indicated by a dot. Branch - a branch is a single or group of components such as resistors or a source which are connected between two nodes. Loop - a loop is a simple closed path in a circuit in which no circuit element or node is encountered more than once. Mesh - a mesh is a single open loop that does not have a closed path. No components are inside a mesh. Components are connected in series if they carry the same current. Components are connected in parallel if the same voltage is across them.
Kirchoff's Law Kirchoff's First Law - The Current Law, (KCL) "The total current or charge entering a junction or node is exactly equal to the charge leaving the node as it has no other place to go except to leave, as no charge is lost within the node". In other words the algebraic sum of ALL the currents entering and leaving a node must be equal to zero, I(exiting) + I(entering) = 0. This idea by Kirchoff is known as the Conservation of Charge. Here, the 3 currents entering the node, I1, I2, I3 are all positive in value and the 2 currents leaving the node, I4 and I5 are negative in value. Then this means we can also rewrite the equation as; I1 + I2 + I3 - I4 - I5 = 0