Kirchoff's first law
The sum of currents entering a junction is equal to the sum of currents leaving the junction.
This is due to the conservation of charge - charge cannot be created or destroyed.
We can write this as:
Example
Section titled “Example”At a junction, three currents meet. Two of the currents are entering the junction
with values of
- Sum of currents entering the junction:
- So the current leaving the junction must also be
due to Kirchoff’s first law.
Sum of all currents
Section titled “Sum of all currents”Kirchoff’s first law can also be expressed as: