21.3 Kirchoff's Laws
The analysis of the flow of currents and potential difference across various parts of an electrical circuit
can be done by using Kirchoff's Laws.
Kirchoff's First Law
At any junction in any electrical circuit the algebraic sum of currents is always zero. The incoming
currents at the junction are considered to be negative and the outgoing currents from the junction are considered
to be positive.
Figure 1
The first law of Kirchoff is therefore a convenient representation
of charge conservation.
Kirchoff's Second Law
The work done on any positive test charge 'q' in moving it around a closed loop is always zero.
where V_{i} is the potential difference across the
i^{th} part of the closed loop. It is obvious that
V_{i} will be positive and negative by equal amounts around the closed loops; since V ´
q is a work done, this law is representation of the law of conservation of energy in the context of electric circuits.
