1. The algebraic sum of the currents at a junction is zero. In other words there is no build up of charge at a junction 2. The sum of the changes in potential round a closed circuit must be zero. Rule 1 is about charge conservation while rule 2 is about energy conservation. |

Rule 1

At the point B there is a junction

Current flowing from the cell (I) = Current in R

Rule 2

Round loop A,B,C,D,E: p.d across cell = - p.d across R

This represents a gain of potential in the cell but a loss in R

Round loop B,C,D,B: p.d across R

In this equation there is a minus because we are moving 'against' the current in R