Custom Search

Voltage divider rule

Voltage divides in series circuit only. In parallel circuit voltage remains same. All of the loads are connected parallelly across voltage source so that loads have two common points with source positive and negative terminals.

same voltage in parallel connection

Considering above circuit three resistors are connected parallelly with source of 220V. Question is what the drop voltage is across three resistors 10, 20 and 30 ohms? The answer is 220V of course. Because three resistor’s positive terminals are connected with the source positive terminal and negative terminals are connected with source negative terminal so voltage remains same at parallel circuit.

In our household the total circuit is connected parallelly so all the electronic devices get same voltage and they can use their full power. If we connect some same power bulbs in series, one bulb will give shining light, second bulb will give less light and third one will less more light because here voltage divides. TV, fridge, bulb, fan etc all are connected in parallel and they take current according to their requirement. Series connection means voltage division and parallel connection means current division.


rule of voltage division


If we connect the same resistors in series then voltage will not same it will divide according to resistor value. We know current flows positive terminal to negative terminal. It is the concept of electrical engineering. Science concept is current flows from negative to positive terminal. Actually positive charge has more mass than electron so it does not move; electron moves and comes to positive charge to neutral it. So we can say 30ohm resistance has more voltage than other two resistors, then 20ohms voltage and 10ohm resistor gets less voltage than other two resistors.

Voltage divider formula


voltage divider formula


Voltage divider rule is that rule if a series circuit has more than one resistor; the voltage across of each resistor is the ratio of resistor value multiplied with voltage source to total resistance value.

Let us consider above circuit there is three resistances. We have to find out each resistance voltage. Using voltage divider rule,


potential divider rule

It is also know as voltage formula.

Example of voltage divider rule: Example of Voltage divider rule

For example of voltage divider rule now we will solve the simple circuit has 6V source and 200 ohm, 100 ohm resistance. We will find voltage drop across each resistance.

Applying formula,

Voltage across 100Ω resistance V1 = (100*6)/(200+100) = 2V

Voltage across 200Ω resistance V2 = (200*6)/(200+100) = 4V


Current divider rule

Series circuit same current, parallel circuit current division. Current remains same in series circuit. It only divides in parallel circuit.


same current at series connection


Considering above circuit there are three resistance R1 , R2 , R3 connected in series having same current I. They are experiencing same current although voltage is different.

We know current is flow of charge per unit time through conductor. Equation of current is I = Q/t .

Let us consider the conductor of this circuit carries 100 C charges per second. Here first resistance prevents flow of charge rate then second resistance gets less charge than first one and third one gets more less than first two resistances. If we remove first resistance, second resistance will get same flow rate which first one experienced, if we remove first and second resistance third one will experience same flow of charge which first one observed. In a word we can say flow of charge remains constant either any of resistance is added or removed. So flow of current remains same for series circuit. Current divides parallelly.


current divider formula


We see here in figure I current are coming and divided into I1 and I2 via two resistance.

The formula of current divider rule is


formula of current divider


The current of each resistor is the ratio of multiplication of total current and opposite resistor value with total resistance.

In our household current divider rule is applied. We use different types of electronic devices. Some of them need small current some of them need huge current. When they are connected in parallel there is no clash between them. No one effects others power taking system. They take current as required. If they are in series then they will not independent. As parallel connection all are independent and takes current as need. Current divider rule is only applicable for two resistors when many resistors are connected in parallel some other methods will be applied to find each current value.

Example of current divider rule:


example of current divider


A circuit caring I current and divides across two resistors viz. 10Ω and 15Ω .

According to current divider rule,

Current for 10Ω resistance, I1 = (15*I)/(10+15) = 15I/25 = 0.6I

Current for 15Ω resistance, I2 = (10*I)/(10+15) = 10I/25 = 0.4I

Share this Story
  • Voltage divider rule

    Voltage divides in series circuit only. In parallel circuit voltage remains same. All of the loads are connected parallelly across voltage ...
Load More Related Articles
  • Electrical Ohm’s Law

    In 1826 famous German scientist Gorge Simon Ohm invented a relation between voltage and current. He expressed the relation in a ...
  • Force on a Current Carrying Conductor in a Magnetic Field

    We know moving charge experiences a force due to magnetic field. Magnetic field creates force into conductor passing current through it. ...
  • Wheatstone Bridge

    Wheatstone bridge is a bridge where four resistances are used. First and second resistance are connected in series; third and fourth ...
  • Biot Savart Law

    To understand completely Biot Savart Law some important rules or laws should be known are Maxwell cork screw Law, Fleming’s right ...
  • Electrical Shunt

    Galvanometer is very sensitive device. Flow of huge amount current can burn galvanometer or displaces spring of it. For saving galvanometer ...
  • 1st Law of Thermodynamics

    Scientist Rumford and Joule did experiment in thermodynamics. In 1847 Joule showed relation between heat and mechanical energy. He explained from ...
Load More By Md Ebrahim Shah
  • Voltage divider rule

    Voltage divides in series circuit only. In parallel circuit voltage remains same. All of the loads are connected parallelly across voltage ...
  • Kirchhoff’s law

    Kirchhoff gave two laws for current and voltage. First law is called KCL and second law is called KVL. Kirchhoff’s current ...
  • Norton’s theorem

    American engineer Norton explained his theorem in 1926 after 43 years publishing Thevenin’s theorem. Norton’s theorem is similar to Thevenin’s theorem. ...
  • Thevenin’s theorem

    Practically always occurs that a particular element like load is always variable when the other elements are fixed in a circuit. ...
  • Inductor

    An inductor is a passive two terminal element designed to store energy in its magnetic field. Inductor also called reactor or ...
  • What is capacitor?

    A capacitor is an element which stores charges. It is a passive element as it stores energy. Michael Faraday invented capacitor. ...
Load More In dc circuits

Check Also

Electrical Ohm’s Law

In 1826 famous German scientist Gorge Simon Ohm ...

© Copyright 2009-2017, All Rights Reserved.