Voltage Drop Formula

Voltage Drop Formula

Voltage drop is the reduction in electrical potential along an electrical current’s path in a circuit. Because some energy supplied is lost, voltage drops in the source’s internal resistance, across conductors, across contacts, and across connectors are undesirable. The power that can be converted in that load to another useful form of energy is directly proportional to the voltage drop across the electrical load. This is explained better with Voltage Drop Formula. The Voltage Drop Formula is critical and important for students who want to take up engineering after school. The Voltage Drop Formula is a critical aspect of the electrical engineering curriculum. Students should focus on Voltage Drop Formula and related topics.

For instance, a ten ohm electric space heater and the wires that supply it might each have a resistance of 0.2 ohms, or about 2% of the circuit resistance. This indicates that the wire itself loses about 2% of the voltage supplied. A space heater may perform poorly due to an excessive voltage drop, and the wires and connections may become overheated.

Voltage Drop

It describes the reduction in electric potential along a current’s path as it flows through an electrical circuit. Additionally, it is a procedure related to an electric circuit. Additionally, a voltage can be assigned to each point in the circuit that is proportional to its so-called “electrical elevation.” The voltage drop is the mathematical difference between a higher voltage and a lower voltage, to put it simply. The explanation becomes simple when students learn about the Voltage Drop Formula. The theoretical explanation along with the Voltage Drop Formula is important because students won’t know what might appear in the examinations.

It is significant for students to have a good preparation for the examinations. The school examinations and tests can be challenging, and they need to have a good understanding of topics like Voltage Drop Formula to have an optimum performance in those examinations. These examinations can be made easy with the help of the Extramarks platform. The platform has multiple learning modules and options that can allow students to take a deeper dive into topics like the Voltage Drop Formula.

In addition, the power delivered to a component in a circuit is determined by multiplying the current flowing through the component’s terminals by the voltage drop across its terminals from corner to corner.

How to calculate voltage drop?


Building the circuit and measuring the drop with the voltmeter is one way to address the voltage drop across the circuit component (current measuring device). Additionally, they are made to cause the least amount of disruption to the circuit they are connected to. Additionally, they accomplish this by reducing the amount of current flowing through the voltmeter.


All voltage drops and all current flows in the circuit are known from these equations. Additionally, the engineers can change the values of the various components to produce a final circuit that best applies its principle.

KCL- According to Kirchhoff’s Current Law, there is no net current flowing into or out of any junction of wires in a circuit. KCL equations also express the conservation of charge.

KVL- According to Kirchhoff’s Voltage Law, all closed paths in a circuit will experience zero cumulative voltage drop. Additionally, energy conservation is expressed in its equations.

Voltage Drop Formula

The voltage drop formula shows how electrical current flows through the components of the electrical circuit that do not supply the voltage, condensing the power supplied from the voltage source. Furthermore, because supply energy is lost, the voltage drops across the internal resistances and connectors of the source are undesirable. Additionally, the voltage drop across active circuit components and loads is preferred because the work that is accomplished by the power source is competent.

V = I × Z

V = IZ

Derivation of the Formula

It is important for students to understand the derivation of the Voltage Drop Formula. Students need to pay special attention to the derivation as might appear in the examination.

I = refers to the current in amperes (A)

Z = refers to the impedance in omega (Ω)

V = refers to the voltage drop

Moreover, the single-phase voltage drop formula is given as

VD = 2LRI1000

And three-phase voltage drop formula is given as

VD = 2LRI1000×0.866


L = refers to the length of the circuit

R = refers to the resistance in Omega (Ω)

I = refers to the load current in amperes

There are a lot of components and aspects to cover in the derivation of the formula, but students can learn more about the derivation on the Extramarks platform. The platform has been aiding students with learning material for over a decade now. It has assisted more than 1 million students in becoming better learners.

Solved Example on Voltage Drop

Example 1

Through a circuit, a current of 9A flows through that carries a resistance of 10 Ω. Find the voltage drop across the circuit.



Current = 9A

Impedance Z = 10 Ω

Putting values in the voltage drop formula we get

V = IZ

V = 9 × 10 = 90 V

So, the voltage drop is 90 V.

Example 2

Suppose a lamp has a 15 Ω and 30 Ω connected in a series. Also, a current of 4A is passing through it. So, calculate the voltage drop of the series?


I = 4A

Resistance Z = (15 +30) Ω = 45 Ω

Putting values in voltage drop formula we get


V = 4 × 45 = 180 V.

So, the voltage drop is 180 V.

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