This all-in-one online Series Resistor Calculator finds the resistance of a circuit consisting of any number of resistors connected in series. It can also find the value of the resistor that needs to be connected in series with the other resistors to get the necessary total resistance of this circuit.
You can enter the values of any known parameters in the input fields of this calculator and find the missing parameter. To add more resistors you can click the “+” symbol on the right hand side. You can also click the “–” symbol to delete extra lines.
Series Resistors Formula
Resistors are in series when they are connected head-to-tail so that the same amount of current flows through each of the resistors. Resistors in series can be represented as the following diagram, where \(R_{1}\), \(R_{2}\), …, \(R_{n}\) are the resistance values of the resistors connected in series.
An important property of a circuit consisting of resistors connected in series is that all the resistors conduct the same electric current. This means that according to Ohm’s law, the voltages across each resistor \(V_{i}\) is equal to the product of that common current \(I\) by the resistance of this resistor \(R_{i}\):
$$V_{i} = R_{i} \cdot I.$$
The total voltage across the circuit of the series resistors is equal to the sum of the voltages across the individual resistors. From this it is easy to show that the following formula is valid for the total equivalent resistance \(R_{T}\) of the entire circuit of resistors connected in series:
$$R_{T} = R_{1} + R_{2} + … + R_{n}.$$
In other words, the total resistance of all the resistors connected in series is equal to the sum of the resistances of these resistors.
In practice, it is sometimes necessary to find the resistance value of the resistor that should be connected in series with the existing resistor of known resistance to get the necessary total resistance.
The solution to any such problem can be easily found using our Series Resistor Calculator.
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Check out our other physics calculators such as Ohm’s Law Calculator or Parallel Resistor Calculator.