Kirchhoff’s current law KCL states that the total current entering a node (point in the circuit where multiple components meet) is always the same as the total current leaving that node.

Suppose a node with five components meets, two of them are providing power and the other three are consuming power as shown in the diagram. According to KCL, the current provided by those two power sources will equal the current consumed by these three power-dissipating components.

$\sum{I_{Entering}= \sum{I_{Leaving}}}$

I$_{1}$ + I$_{2}$ = I$_{3}$ + I$_{4}$ + I$_{5}$

Note the direction of the current in the diagram. The two currents I_{1} and I_{2} are entering the node at point P. And three currents are leaving the node.

- What is Transistor hFE? Current Gain in a Transistor
- Steps in Electrical Failure Analysis for High-Speed Communication

The KCL holds for DC circuits as well as AC circuits and linear and non-linear components.

Gustav Kirchhoff was a German physicist, who presented two laws. The Kirchhoff’s Current Law (KCL) and Kirchhoff Voltage Law (KVL). Ohm’s law is very basic, which may not be sufficient to analyze a complex circuit. Kirchhoff’s Current Law (KCL) provides the basis for Nodal Voltage Analysis.

## Example:

Suppose a node with three wires is connected, if one of them is providing a current of 4A and the second is the wire is taking a current of 4A.

What would be the current of the third wire? And what would be the direction of the current?

### Solution:

Let’s draw the diagram representing the directions of the current.

According to the KCL, the entering current will always be equal to the leaving current, i.e.

$I_{entering}=I_{leaving}$

The unknown current is entering the node :

$4A+I=4A$

$I=4A-4A=0A$

The unknown current is zero.

## Limitations Of KCL :

Kirchhoff’s Current law assumes that current flows only in conductors, but in the case of high-frequency circuits, current can be caused by parasitic capacitance without any conductor.

### Short Answer Questions

### How to find current using Kirchhoff’s law?

To find current using Kirchhoff’s Current Law (KCL), set up equations at junctions in a circuit. The sum of currents entering a junction equals the sum of currents leaving it.

- Breaker Size Calculator: AC and DC Circuit Breaker Sizing Calculator
- Understanding Light Switch Sparks: Causes, Risks, and Safety Measures

### Can Kirchhoff’s current law solve for voltage?

No, Kirchhoff’s Current Law deals with currents in a circuit. It states that the total current entering a junction equals the total current leaving, focusing on current conservation.

### Does Kirchhoff’s law apply when the current not flowing?

Kirchhoff’s laws apply to electric circuits under steady-state conditions, where currents and voltages are constant. If there is no current flowing in a specific branch or part of the circuit, that branch can be treated as an open circuit, and Kirchhoff’s laws are still applicable to the rest of the circuit. However, in dynamic situations or when dealing with transient states, the application of Kirchhoff’s laws might need to be adjusted.