Kirchhoff’s Law

Kirchhoff’s Laws come in handy while dealing with circuits, voltage, and current. These laws play a crucial part in analysing circuits. In 1845, Gustav Kirchhoff described Kirchhoff’s Law. He was a German physicist who also contributed to the field of electrical circuits, black body radiation, and spectroscopy. Kirchhoff’s Laws mainly focuses on quantifying the current flow through an electrical circuit and the varying voltage around the circuit loop. Both Kirchhoff’s circuit laws are used in analysing electrical circuits. By the end of this article, you’ll have a good understanding of Kirchhoff’s Law and the process of analysing an electrical circuit using the laws.

Kirchhoff’s Current Law

All electrical circuits have a current flowing through them. The current flows when the carriers travel around the electrical circuit. Kirchhoff’s Current Law mainly focuses on the current flowing through the node or a junction. Kirchhoff’s Law states that the current rushing in the node should be similar to the current flowing out of it. Kirchhoff’s Current law can be expressed as:

∑iIn    =∑iout

Concept

For better understanding, let’s set up three wires that are supposed to meet at a singular junction. After this, notice if the current is flowing in the same direction. If it is, then the current is positive. However, if the current is flowing in opposite directions then the current is said to be negative. Current is measured in milliamps, mA. 

If the current is positive, then Kirchhoff’s Laws can be expressed as:

I1​+I2​=I3​(I representing a current)

If the current is negative, then Kirchhoff’s Laws can be expressed as:

I1​+I2​+I3​=0 (This is because one of the currents would be negative)

Kirchhoff’s Current Law also has a general expression:

k=1nIk=0

Exceptions

In theory, there are no exceptions to Kirchhoff’s Current Law. While electrons repel each other within a conductor, electrons in an insulator might get stuck (a static charge). Static charge can accumulate within a circuit. 

Kirchhoff’s voltage law

Kirchhoff’s Voltage Law mainly focuses on the voltage and the electrical circuit. The Law says that the aggregate of voltages within a loop is always zero. Kirchhoff’s Voltage Law can also be expressed as:

k=1nVk=0

(Here n is the total voltages measured)

Concept

As mentioned above, carriers flow throughout the circuit. During this, they gain and lose electricity varying on the element in the circuit. This is because of the work and energy put in by these elements. The work completed on the carrier charge by the supply elements (cell) should be similar to the work completed by other components (resistors). If we assume the supply elements to be positive and the other components to be negative then the aggregate of voltages within the loop would be zero. This process can be a bit repetitious and will require patience as it can lead to great results. Whatever path we choose in the loop, the result will always be the same. For instance, the difference between a person who weighs 60 Kg and a person who weighs 50 Kg is always going to be 10 Kg.

Properties of Voltage Law:

• The loop can begin from any junction or node in the circuit. Just remember to complete the loop so the aggregate of the voltage would result in zero.
• The loop can be either counterclockwise or clockwise.
• If the electrical circuit has numerous loops, then the Law would apply to every one of them.

Exceptions

An exception to Kirchhoff’s Voltage Law is in Maxwell’s equations. The equations state that the voltage generated within the loop is equivalent to the rate of shift of magnetic flux through the surface enveloped by the circuit. There is only one possibility for the voltage around the loop to be zero – there should be no magnetic flux. 

Kirchhoff’s Law is still applicable, however, we sometimes make adjustments according to the situation. There may be a problem when you are working with ground loops as they tend to develop large surfaces for time-varying magnetic flux.

Conclusions

To conclude, you can utilise Kirchhoff’s Law to analyse your electrical circuit and notice the properties and functioning of an electrical circuit. These laws are extremely significant in our daily life as they describe how the electrical current flows in our electronic devices and appliances. They depict the flow of energy and current within a loop. These laws are at the centre of circuit analysis. For analysing an electrical circuit, we require supply elements and other components such as cell, resistor, and inductor. We also need these two laws. For precise analysis be attentive towards voltage and current within the loop.