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If you need more voltage divider informationRead on because we will show you the formula, solved exercises and more.
What is a voltage divider?
A voltage divider is a circuit used to divide an electrical voltage between one or more resistors connected in series.
The simplest voltage divider circuit is the one below. In it you can see a voltage source (Vcc) that divides its voltage between resistors Rs (V1) and R2 to which corresponds a voltage value V2.
Since we have a series connection of resistors, the current flowing through them is the same but the voltage is distributed. Due to this configuration, we can calculate an equivalent circuit in which there is only a single resistance Req which will be the equivalent resistance of all the resistors connected in series.
Voltage divider formulas
Since there are quite a few variables involved in the voltage divider, let's look at all the variables involved in the voltage divider. formulas for calculating different voltages, resistances, powers and currents.
The equivalent resistance (Req) of a voltage divider is measured in Ohms is calculated as follows:
Req = R1 + R2
The current is the same at all points of the circuit. by the series configuration of the impedances or currents.
In case we do not know its value, we can calculate the current in a voltage divider with this formula:
I = Vin / (R1 + R2)
Basically what we do is to divide the input voltage by the value of the equivalent resistance (R1 + R2).
As this is a series configuration, each resistive element will have a different voltage drop based on their value.
We have the value of R1 and R2 as well as the value of the current, therefore, we apply the Ohm's Law and we are left with:
V1 = I x R1
V2 = I x R2
As for the output voltage or Vout, we obtain its value with the following formula:
Vout = R1 x Vin / (R1 + R2)
Pay attention to the placement of the name of the resistors in the circuit to avoid making mistakes.
Now that you know how to calculate all the unknowns at the different points of the circuit, you are able to solve any voltage divider even with three resistors or more resistive elements. Anyway, if you have any doubt, write us a comment and we will help you to solve your questions.
Solved exercises of the voltage divider
We are going to see a example of voltage divider with a solved exercise in which we are asked to calculate:
- The output voltage (Vout)
- The current flowing in the circuit (I)
- The voltage drop of each resistor (V1 and V2)
First of all we are going to calculate the Intensity:
I = Vin / (R1 + R2) = 20V / (9000 Ω + 1000 Ω) = 0.002 A = 2 mA
The following calculate the voltage drop of each resistor:
V1 = I x R1 = 2 mA x 9 KΩ = 18 V
V2 = I x R2 = 2 mA x 1 KΩ = 2 V
If you notice, V1 + V2 is equal to the input voltage so it is already a clue that we are solving the voltage divider exercise correctly.
Finally, we calculate the output voltage Vout:
Vout = 1 KΩ x 20V / (9 KΩ + 1 KΩ) = 1 KΩ x 20V / 10 KΩ = 2V
Voltage divider calculator
The voltage division calculator allows you to automatically solve exercises by simply entering the values of the input voltage in Volts and the resistors R1 and R2 in Ohms.
After pressing the calculate button you will automatically obtain values such as current, equivalent resistance, V1, V2, Vout and power values for each resistor.
If you have any questions, write us and we will help you!