Why metal has a high resistance

Electrical resistance

Electrical resistance is simply explained in this article. Summary of the content:

  • A Explanationwhat an electrical resistance is.
  • Lots Examples all about resistances and their calculation.
  • tasks / Exercises for calculating resistances.
  • A Video, which deals with resistance in electrical engineering.
  • 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: resistance of electrical engineering

In the basics of electrical engineering you learn that there are electrical charges. When these move, you get an electric current. It is driven by an electrical voltage. However, there is something else that is hindering the movement of the load. And already we are with electrical resistance. To the definition:


Charges collide - for example in the metallic conductor - against the ions of the metal lattice and these hinder their movement. This is known as electrical resistance. The greater the disability, the greater the resistance. Basically every conductor and every component or device has a resistance. Sometimes electrical resistances are not welcome. In other cases, one might want to intentionally create resistance. That is why there are electrical resistances as components.

The weight of a person is usually given in kilograms and the length of a car in meters. But how do you state the electrical resistance? Answer: In ohms (Ω). A resistor can be 100 Ω, for example. The symbol is an "R". When speaking in a formula, an indication in ohms is used for "R".

Resistance formulas:

As you may already know, there is a relationship between current, voltage and resistance. If not, let's take a look at the formula behind Ohm's law.

Or expressed in words:

Summarize resistances:

Sometimes there are multiple resistors in a circuit. In this case one is often interested in the total resistance. There are two typical cases (there are more, but these are less common).

The first case is called Series connection or Series connection. The resistors are one behind the other, so the moved charges "flow" one after the other through the resistors:

If we have such a case then you simply add all resistances together.

Another case is when the current splits up to "flow" through resistors. This is called Parallel connection. For two resistors it looks like this:

For two resistors, the total resistance can be calculated as follows:

There are many other options for arranging resistors, for example three or more resistors in parallel, a mixture of series and parallel connections or star and delta connections. We will cover this in further articles. The resistance of wires is also dealt with.


Examples of resistance

In this section, a number of examples of resistances are to be calculated.

example 1:

Given a voltage of 8 V and a current of 2 A. How big is the resistance?


Example 2:

Two resistors are connected as follows. How big is the total resistance?


We have a series connection here. So we can simply add up the resistances.

  • R = R1 + R2
  • R = 13 Ω + 21 Ω = 34 Ω

Example 3:

Two resistors are connected as follows. How big is the total resistance?


Here we have a parallel connection with two resistors. Hence we take the corresponding formula from above. Here we use the two resistors. We multiply in the numerator and add in the denominator. At the end we calculate the fraction or remove one ohm. This brings us to about 7.33 ohms.

Tasks / exercises in electrical resistance


Videos on resistance

Electrical resistance video

This video is about electrical resistance. It's about what a resistance actually is. Then it comes to Ohm's law and some examples with numbers and units. Be sure to check it out.

Next video »

Questions with answers about resistance

This section deals with typical questions about electrical resistance.

Q: How important are resistors in electrical engineering?

A: Very important. To be honest, I can't think of any circuit in my professional life that would have done without electrical resistors. They are needed in numerous places, from dividing voltages to wiring operational amplifiers.

Q: What other topics should I check out?

A: For the basics of electrical engineering and magnetism, you should still have a look at these topics: