This is how you cause problems with series parallel connections

Series connection / series connection of resistors

We will deal with the series connection of resistors in this article. Summary of the content:

  • A Explanationwhat is meant by the series connection of resistors.
  • Some Examples to calculate with Ohm's law.
  • tasks / Exercises so that you can practice this basic law of electrical engineering.
  • A Video, which deals with Ohm's law.
  • A Question and answer area around this topic

This article is part of our electrical engineering course "From the basics of electrical engineering in 5th grade to becoming an engineer".

Explanation of series connection resistors

First a quick note: A series connection of resistors is sometimes also referred to as a series connection of resistors. Now what is a series connection?


A series connection of resistors is a special arrangement of resistors. There are two or more resistors in a row through which the same current flows. Voltage drops across every resistor.

In the simplest case we have two resistors in a row. It can look like this:

In the next graphic you can see a series connection of three resistors in an electrical circuit.

Now a little problem arises. For example, if you want to use Ohm's law, an "R" appears in the formula for the resistance. However, we have several obstacles here. For this reason we have to be able to make a total resistance out of the individual resistors. The formula to summarize a series connection looks like this:

In other words: just add up all the resistances.

For comparison, let's look at a parallel connection. This looks like this:

As you can see: This is where the line branches out, the current splits and one part flows through the upper resistor and the other part of the current flows through the lower resistor. We hang on to:


In the case of a series connection, the current flows through all resistors in this series connection. The current is always the same. In the case of parallel connection, the line is divided and the current is distributed over two or more lines and only part of the current flows through each resistor.

In the next section we look at examples of daisy chaining.


Examples of series connection

The next examples show where the series connection can be used and how to calculate with it.

example 1:

Consider the next circuit with three resistors in series. The voltage source supplies 5 volts. The resistances are 10 ohms, 25 ohms and 40 ohms. How much current is flowing in the circuit?


In order to be able to use Ohm's law formula U = R · I, we must first calculate R. To calculate the total resistance R, we add the three resistances together. We get 75 ohms as a result. We convert the equation for Ohm's law according to the current. We put the voltage at 5 V and the resistor at 75 ohms and we get a current of 0.0666 amps.

Example 2:

Consider an electrical circuit with a series connection of two resistors. A current of 0.12 amps flows. How much voltage does each resistor drop? How much voltage does the voltage source deliver? Then think about how you can check the result.


The current of 0.12 amps flows through both resistors. We apply Ohm's law formula to both resistors and thus obtain the voltages that drop across the respective resistors. We denote everything that has to do with the first resistor with the index 1, the second resistor with the index 2. We add these two voltages, because the voltages that drop across the two resistors naturally correspond to what the voltage source has to supply .

The voltage source delivers a voltage of 7.2 V. Have we miscalculated now? We do the math for checking / testing. We put in the equation of Ohm's law the sum of the two resistances and also the current of 0.12 A and get 7.2 V.

Exercises Series connection of resistors


Daisy chain video

Basics of electrical engineering

The next video covers the basics of electrical engineering. In addition to Ohm's law and the fundamentals for it, series connection and parallel connection are also dealt with. This not only gives you an insight into the series connection, but also gives you a complete insight into the topic.

Next video »

Questions with answers in series

In this section, we'll look at questions with answers about daisy chaining.

Q: Is there still everything a series connection or a parallel connection?

A: In principle, you can set up all kinds of series connections or parallel connections. Here are a few examples

  • For batteries and accumulators there is a series connection and a parallel connection.
  • You can also connect lamps or LEDs in series or in parallel.
  • Capacitors or coils are also included.