Unit – I Basic Circuits Analysis

Ohm’s Law In the period 1826 to 1827, a German physicist, Georg Simon Ohm, found the relationship between voltage, current and resistance which is referred to as Ohm’s law.

Ohm’s Law – Statement Ohm’s law states that the current, I flowing in a circuit, is directly proportional to the applied voltage V at constant temperature.

Ohm’s Law – Understanding

Resistance The resistance R of any element denotes its ability to resist (or oppose) the flow of electric current. It is measured in ohms (Ω). Conductors are materials which permit the flow of current. But they do resist the flow of current.

The resistance of a material depends on Type of material Length of the conductor Cross-sectional area Temperature The resistance of a conductor at a given temperature is

Limitations of Ohm’s Law Not applicable for varying temperature conditions. Not all resistors obey Ohm’s law. A resistor that obeys Ohm’s law is known as a linear resistor. A nonlinear resistor does not obey Ohm’s law. Characteristics of linear and non linear resistor are shown below.

Electric Circuit

Classification of Circuit Elements Circuit elements are classified into Active elements Passive elements A passive element is an electrical component that does not generate power, but instead dissipates, stores, and/or releases it. Passive elements include resistances, capacitors, and coils (also called inductors).

Active Elements Active elements supply power to an electrical circuit. Example: Voltage source and current source

Passive Elements A passive element either stores or dissipates the energy received from active elements. Passive elements include resistances, capacitors, and inductors.

Classification of Electrical Networks Linear and Non linear Network Bilateral and Unilateral Network Lumped and Distributed Network

Nodes, Branches and Loops

Laws introduced by Kirchhoff Kirchhoff’s Laws Gustav Robert Kirchhoff (12th March 1824 – 17th October 1887) was a German physicist. He introduced Kirchhoff’s laws in the year 1847. Laws introduced by Kirchhoff Kirchhoff’s current law or point law Kirchhoff’s voltage law or mesh law

Kirchhoff’s Current Law or Point Law Kirchhoff’s first law is based on the law of conservation of charge. Algebraic sum of currents entering a node is equal to the algebraic sum of currents leaving the same node.