When we have several resistors in an electrical circuit, the **equivalent resistance**, becomes a single resistor that could replace all the others in a simplified circuit. If you want to know more about this, keep reading to know everything about the **Equivalent resistance** and the calculations of it.

## What is an equivalent resistance?

We must bear in mind that the value of the electrical resistance, with respect to the aforementioned, to make it really balanced, it has to be such that the voltages, currents and total resistances of some circuit are the same as those of a original circuit with all the original resistors, so they are the conditions for it to be really equivalent.

Likewise, you must remember that the equivalent electrical resistance is basically a single resistance that replaces others to simplify the calculations within the circuits. Therefore, it is a mathematical skill through which it is possible to study the behavior of a circuit through another easier with a single resistor.

### Equivalent resistors in series

If we have a circuit with two or more resistors in series it is equivalent to another with a single resistor whose value is the sum of all the resistors in series and will be called Total Equivalent Resistance. If, for example, we are presented with 3 resistors in series as in the previous image, in order to calculate their equivalent or total, we only have to add them:

- Equivalent Re = 10 + 5 + 15 = 30Ω

Therefore the voltage will remain 6V. The equivalent Re would be the total resistance of the circuit, and if we calculate the total intensity of the circuit it would be the same as the first circuit that is called equivalent circuit. It is necessary to bear in mind that saying equivalent does not mean that it is the same, they are different but equivalent circuits, since their total voltage, total resistance and total intensity are the same.

Within an equivalent circuit, applying Ohm's Law, the total current of a circuit is obtained as a result, calculating: I total = VT / Rt = 6/30 = 0,2A. This will be the same in both circuits. So now, to be able to solve the first circuit it is simpler, since we know how much the total intensity of a circuit is worth, thanks to the **equivalent resistance **that we have calculated through the second circuit.

### Equivalent resistance in parallel

Within parallel circuits, calculating resistance would be a bit more complicated, but not to die for. If we have an equivalent resistance of several resistors in parallel, we must calculate it with the formula of:

- Rt = 1/1-R1 + 1-R2 + 1-R3 +…

Although it looks more complicated than being in series, it must meet the conditions of being equivalent through said formula. By substituting the values of R1, R2 and R3, the equivalent resistance is calculated; Equivalent Re = 2,73, taking into account that the total resistance in parallel current will be less than in series.

On the other hand, if the total intensity of the circuit is calculated, the calculation that you give us will be the same as that of the previous circuit with the 3 resistances: Itotal = Vt / Rt = 5 / 2,73 = 1,83A.

Now we can calculate the currents at each point in the first circuit since we know the voltage in each branch (5V in it because it is in parallel) and we know the resistance in each branch (R1, R2 or R3).

- I1 = V / R1; I2 = V / R2; I3 = V / R3; The sum of the 3 intensities will have to be the same as the Itotal calculated previously.

If this article has been helpful, we invite you to see more information about electronics from our website, such as Normalized powers What are they and how many types are there? We will also leave you the following video so that you can learn more about this topic.