question_answer

Directions : (31-35)

Kirchhoff's Rules

In 1942, a German physicist Kirchhoff extended Ohm's law to complicated circuits and gave two laws, which enable us to determine current in any part of such a circuit.

According to Kirchhoff's first rule, the algebraic sum of the current meeting at a junction in a closed electric circuit is zero. The current flowing in a conductor towards the junction is taken as positive and the current flowing away from the junction is taken as negative.

According to Kirchhoff s second rule, in a closed loop the algebraic sum of the emfs and algebraic sum of the products of current and resistance in the various arms of the loop is zero. While traversing a loop, if negative pole of the cell is encountered first, then its e.m.f. is negative, otherwise positive..

Kirchhoff's Ist law follows :

A) law of conservation of energy

B) law of conservation of charge

C) law of conservation of momentum

D) Newton's third law of motion