Gustav Robert Kirchhoff

                                                       Gustav Robert Kirchhoff(1824-1887)

The fundamental contributions of German physicist Kirchhoff were in the fields of black body radiation and spectroscopy. But he also contributed in many other fields. his rules that you will study in this lesson enable us to analyse complex electric networks. Whit the help of Bunsen spectrum analysis, he discovered elements Rubidium and Cesium. Two Rules of Gustav Robert Kirchhoff. we know that Ohm's law give current-voltage relation for resistive circuits. But when the circuit is complicated, it is difficult to know currrent distribution by Ohm's law. In 1842, Kirchhoff formulated two rules which enable us to know the distribution of current in complicated electrical circuits or eelectrical networks
Rules one: It states that the sum of all currents directed towards a junction (point) in an electrical network is equal to the sum of all the currents directed away from the junction.

Rules Two: This rule  is an application of law of conservatio of energy for electrical eircuits. It tells us that the algebrac sum of the products of the currents and resistances in any closed loop of an electrical network is equal to the algebraic sum of electromotive forces acting in the loop.
While using this rule, we start from a point on the loop and go along the loop either clockwise or
anticlockwise to reach the same point again. the product of current and resistance is taken as positive when we traverse in the directio of current. the e.m.f is taken positive when we traverse from negative to positive electrode thruough the cell. Mathematically,