Voltage division is a concept that must be understood by people carrying out electrical projects, whether they are students, hobbyists, or professional engineers.
An Introduction to Voltage Drop
You might have heard of the term “voltage drop”, which refers to the reduction in electrical potential (voltage) that happens as current flows through a circuit.
This occurs because all electrical conductors, such as wires and cables, have some resistance to electricity flow. As a result of this resistance, there is a loss of energy, manifesting as a fall in voltage across the circuit.
Voltage Dividers Are an Inherent and Deliberate Cause of Voltage Drop
Although voltage drops can happen accidentally – for example, due to such factors as excessive load or poor connections – they are also often expected and designed into circuits.
Voltage division is a good example of a situation in which voltage drop is deliberate, given that it inherently has this effect.
A voltage divider circuit typically comprises two resistors in series. It is specifically designed to create a lower output voltage than the input voltage, which it achieves by distributing the voltage across the resistors.
In such a circuit, the output voltage is below the input voltage due to it being a fraction of the total voltage, determined by the ratio of the resistors.
What Is the Voltage Divider Formula?
Presuming a two-resistor circuit is involved, the voltage divider formula can be expressed as Vout = Vin * (R2 / (R1 + R2)).
For the purposes of this formula:
- Vout is the voltage being sought, measured across the resistor R2
- Vin is the input voltage being supplied to the circuit
- R1 and R2 are the resistance values of the two resistors in the series circuit
In summary, the voltage divider formula divides the input voltage by the ratio of the second resistor’s resistance to the total resistance of both resistors.
Manual Calculations vs Online Tools for Figuring Out Voltage Drop
At this stage, you may be thinking: couldn’t you just use an online tool for calculating voltage drop across resistors, instead of depending on time-consuming and error-prone manual calculations?
It is true that reputable voltage divider calculators can be invaluable for verifying the accuracy of manual calculations.
However, it is equally true that getting to grips with both methods can greatly help deepen your understanding of how voltage is distributed in a series circuit. It can also be very useful for guarding against errors and troubleshooting in a wide range of scenarios.
How Can You Apply the Voltage Divider Formula to A Practical Context?
Here, then, is a quick rundown of the steps you can take to use the voltage divider formula within a given electrical project:
- Make Sure the Circuit Is a Series Circuit
Given that the voltage divider rule applies exclusively to series circuits, you should first double-check that with your own circuit, the resistors are genuinely connected end-to-end (“in series”).
- Gather The Required Information
To undertake the calculation using the voltage divider formula, it will be necessary to know the input voltage (Vin) and the resistance of each resistor (R1, R2). You will also need to be sure which resistor’s voltage you need to figure out.
- Calculate Total Resistance
This stage simply entails the resistance of all series resistors in the circuit being added together to produce a total resistance reading. So, following the above example where there are two resistors, the calculation would be R1 + R2.
- Apply The Voltage Divider Formula
For the resistor of interest, calculate the voltage using the formula we set out earlier: Vout = Vin * (R2 / (R1 + R2)). Make sure you use consistent units, including volts for Vin and ohms for resistances.
- Verify The Calculation
To touch on what we said earlier: verify the result with a calculator to help guard against any errors with the manual calculation. Check, as well, that the voltage across all resistors equals the input voltage.
That’s it – well, for this guide, anyway. To learn more about the practical aspects of using voltage dividers, you may be interested in reading this tutorial for beginners.
